diff --git a/boot.php b/boot.php
index 1e0c300e19..af542e09ad 100644
--- a/boot.php
+++ b/boot.php
@@ -442,6 +442,14 @@ define('SR_SCOPE_ALL',  'all');
 define('SR_SCOPE_TAGS', 'tags');
 /* @}*/
 
+/**
+ * Lowest possible date time value
+ */
+
+//define ('NULL_DATE', '0001-01-01 00:00:00');
+define ('NULL_DATE', '0000-00-00 00:00:00');
+
+
 // Normally this constant is defined - but not if "pcntl" isn't installed
 if (!defined("SIGTERM"))
 	define("SIGTERM", 15);
@@ -2039,7 +2047,7 @@ function proc_run($cmd){
 	}
 
 	// Checking number of workers
-	$workers = q("SELECT COUNT(*) AS `workers` FROM `workerqueue` WHERE `executed` != '0000-00-00 00:00:00'");
+	$workers = q("SELECT COUNT(*) AS `workers` FROM `workerqueue` WHERE `executed` > '%s'", dbesc(NULL_DATE));
 
 	// Get number of allowed number of worker threads
 	$queues = intval(get_config("system", "worker_queues"));
diff --git a/include/Contact.php b/include/Contact.php
index 2aab828f8a..7e8de65131 100644
--- a/include/Contact.php
+++ b/include/Contact.php
@@ -129,7 +129,7 @@ function mark_for_death($contact) {
 	if($contact['archive'])
 		return;
 
-	if($contact['term-date'] == '0000-00-00 00:00:00') {
+	if($contact['term-date'] <= NULL_DATE) {
 		q("UPDATE `contact` SET `term-date` = '%s' WHERE `id` = %d",
 				dbesc(datetime_convert()),
 				intval($contact['id'])
@@ -187,13 +187,13 @@ function unmark_for_death($contact) {
 
 	// It's a miracle. Our dead contact has inexplicably come back to life.
 	q("UPDATE `contact` SET `term-date` = '%s' WHERE `id` = %d",
-		dbesc('0000-00-00 00:00:00'),
+		dbesc(NULL_DATE),
 		intval($contact['id'])
 	);
 
 	if ($contact['url'] != '') {
 		q("UPDATE `contact` SET `term-date` = '%s' WHERE `nurl` = '%s'",
-			dbesc('0000-00-00 00:00:00'),
+			dbesc(NULL_DATE),
 			dbesc(normalise_link($contact['url']))
 		);
 	}
@@ -256,7 +256,7 @@ function get_contact_details_by_url($url, $uid = -1, $default = array()) {
 
 		// "bd" always contains the upcoming birthday of a contact.
 		// "birthday" might contain the birthday including the year of birth.
-		if ($profile["birthday"] != "0000-00-00") {
+		if ($profile["birthday"] >= "0001-01-01") {
 			$bd_timestamp = strtotime($profile["birthday"]);
 			$month = date("m", $bd_timestamp);
 			$day = date("d", $bd_timestamp);
@@ -273,7 +273,7 @@ function get_contact_details_by_url($url, $uid = -1, $default = array()) {
 				$profile["bd"] = (++$current_year)."-".$month."-".$day;
 			}
 		} else {
-			$profile["bd"] = "0000-00-00";
+			$profile["bd"] = "0001-01-01";
 		}
 	} else {
 		$profile = $default;
@@ -309,7 +309,7 @@ function get_contact_details_by_url($url, $uid = -1, $default = array()) {
 		$profile["location"] = "";
 		$profile["about"] = "";
 		$profile["gender"] = "";
-		$profile["birthday"] = "0000-00-00";
+		$profile["birthday"] = "0001-01-01";
 	}
 
 	$cache[$url][$uid] = $profile;
diff --git a/include/cron.php b/include/cron.php
index 2fc8de51c5..26ff728f4d 100644
--- a/include/cron.php
+++ b/include/cron.php
@@ -173,8 +173,8 @@ function cron_update_photo_albums() {
 function cron_expire_and_remove_users() {
 	// expire any expired accounts
 	q("UPDATE user SET `account_expired` = 1 where `account_expired` = 0
-		AND `account_expires_on` != '0000-00-00 00:00:00'
-		AND `account_expires_on` < UTC_TIMESTAMP() ");
+		AND `account_expires_on` > '%s'
+		AND `account_expires_on` < UTC_TIMESTAMP()", dbesc(NULL_DATE));
 
 	// delete user and contact records for recently removed accounts
 	$r = q("SELECT * FROM `user` WHERE `account_removed` AND `account_expires_on` < UTC_TIMESTAMP() - INTERVAL 3 DAY");
@@ -276,7 +276,7 @@ function cron_poll_contacts($argc, $argv) {
 			$xml = false;
 
 			if($manual_id)
-				$contact['last-update'] = '0000-00-00 00:00:00';
+				$contact['last-update'] = NULL_DATE;
 
 			if(in_array($contact['network'], array(NETWORK_DFRN, NETWORK_ZOT, NETWORK_OSTATUS)))
 				$contact['priority'] = 2;
diff --git a/include/datetime.php b/include/datetime.php
index 8d4961cd7c..601b4decf4 100644
--- a/include/datetime.php
+++ b/include/datetime.php
@@ -126,7 +126,7 @@ function datetime_convert($from = 'UTC', $to = 'UTC', $s = 'now', $fmt = "Y-m-d
 	// add 32 days so that we at least get year 00, and then hack around the fact that
 	// months and days always start with 1.
 
-	if(substr($s,0,10) == '0000-00-00') {
+	if(substr($s,0,10) <= '0001-01-01') {
 		$d = new DateTime($s . ' + 32 days', new DateTimeZone('UTC'));
 		return str_replace('1','0',$d->format($fmt));
 	}
@@ -171,7 +171,7 @@ function dob($dob) {
 	$f = get_config('system','birthday_input_format');
 	if(! $f)
 		$f = 'ymd';
-	if($dob === '0000-00-00')
+	if($dob <= '0001-01-01')
 		$value = '';
 	else
 		$value = (($year) ? datetime_convert('UTC','UTC',$dob,'Y-m-d') : datetime_convert('UTC','UTC',$dob,'m-d'));
@@ -339,7 +339,7 @@ function relative_date($posted_date, $format = null) {
 
 	$abs = strtotime($localtime);
 
-	if (is_null($posted_date) || $posted_date === '0000-00-00 00:00:00' || $abs === False) {
+	if (is_null($posted_date) || $posted_date <= NULL_DATE || $abs === False) {
 		 return t('never');
 	}
 
@@ -553,7 +553,7 @@ function update_contact_birthdays() {
 	// This only handles foreign or alien networks where a birthday has been provided.
 	// In-network birthdays are handled within local_delivery
 
-	$r = q("SELECT * FROM contact WHERE `bd` != '' AND `bd` != '0000-00-00' AND SUBSTRING(`bd`,1,4) != `bdyear` ");
+	$r = q("SELECT * FROM contact WHERE `bd` != '' AND `bd` >= '0001-01-01' AND SUBSTRING(`bd`,1,4) != `bdyear` ");
 	if (dbm::is_result($r)) {
 		foreach ($r as $rr) {
 
diff --git a/include/dbm.php b/include/dbm.php
index fedc2e4fdb..eb3e2d0382 100644
--- a/include/dbm.php
+++ b/include/dbm.php
@@ -98,7 +98,7 @@ class dbm {
 
 		// Workaround for 3.5.1
 		if ($timestamp < -62135596800) {
-			return '0000-00-00 00:00:00';
+			return NULL_DATE;
 		}
 
 		// The above will be removed in 3.5.2
diff --git a/include/dbstructure.php b/include/dbstructure.php
index 1e4790de2e..99057a9c00 100644
--- a/include/dbstructure.php
+++ b/include/dbstructure.php
@@ -536,8 +536,8 @@ function db_definition($charset) {
 					"filetype" => array("type" => "varchar(64)", "not null" => "1", "default" => ""),
 					"filesize" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"data" => array("type" => "longblob", "not null" => "1"),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"edited" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"edited" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"allow_cid" => array("type" => "mediumtext"),
 					"allow_gid" => array("type" => "mediumtext"),
 					"deny_cid" => array("type" => "mediumtext"),
@@ -564,7 +564,7 @@ function db_definition($charset) {
 					"k" => array("type" => "varbinary(255)", "not null" => "1", "primary" => "1"),
 					"v" => array("type" => "mediumtext"),
 					"expire_mode" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
-					"updated" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"updated" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("k"),
@@ -613,7 +613,7 @@ function db_definition($charset) {
 			"fields" => array(
 					"id" => array("type" => "int(11)", "not null" => "1", "extra" => "auto_increment", "primary" => "1"),
 					"uid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"self" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"remote_self" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"rel" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
@@ -651,14 +651,14 @@ function db_definition($charset) {
 					"usehub" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"subhub" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"hub-verify" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"last-update" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"success_update" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"failure_update" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"name-date" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"uri-date" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"avatar-date" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"term-date" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"last-item" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"last-update" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"success_update" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"failure_update" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"name-date" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"uri-date" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"avatar-date" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"term-date" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"last-item" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"priority" => array("type" => "tinyint(3)", "not null" => "1", "default" => "0"),
 					"blocked" => array("type" => "tinyint(1)", "not null" => "1", "default" => "1"),
 					"readonly" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
@@ -703,8 +703,8 @@ function db_definition($charset) {
 					"recips" => array("type" => "text"),
 					"uid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"creator" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"updated" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"updated" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"subject" => array("type" => "text"),
 					),
 			"indexes" => array(
@@ -731,10 +731,10 @@ function db_definition($charset) {
 					"uid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"cid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"uri" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"edited" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"start" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"finish" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"edited" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"start" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"finish" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"summary" => array("type" => "text"),
 					"desc" => array("type" => "text"),
 					"location" => array("type" => "text"),
@@ -770,7 +770,7 @@ function db_definition($charset) {
 					"network" => array("type" => "varchar(32)", "not null" => "1", "default" => ""),
 					"alias" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"pubkey" => array("type" => "text"),
-					"updated" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"updated" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("id"),
@@ -811,7 +811,7 @@ function db_definition($charset) {
 					"request" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"photo" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"note" => array("type" => "text"),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("id"),
@@ -838,10 +838,10 @@ function db_definition($charset) {
 					"nurl" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"photo" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"connect" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"updated" => array("type" => "datetime", "default" => "0000-00-00 00:00:00"),
-					"last_contact" => array("type" => "datetime", "default" => "0000-00-00 00:00:00"),
-					"last_failure" => array("type" => "datetime", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"updated" => array("type" => "datetime", "default" => NULL_DATE),
+					"last_contact" => array("type" => "datetime", "default" => NULL_DATE),
+					"last_failure" => array("type" => "datetime", "default" => NULL_DATE),
 					"location" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"about" => array("type" => "text"),
 					"keywords" => array("type" => "text"),
@@ -875,7 +875,7 @@ function db_definition($charset) {
 					"uid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"gcid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"zcid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
-					"updated" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"updated" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("id"),
@@ -923,10 +923,10 @@ function db_definition($charset) {
 					"noscrape" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"network" => array("type" => "varchar(32)", "not null" => "1", "default" => ""),
 					"platform" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"last_poco_query" => array("type" => "datetime", "default" => "0000-00-00 00:00:00"),
-					"last_contact" => array("type" => "datetime", "default" => "0000-00-00 00:00:00"),
-					"last_failure" => array("type" => "datetime", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"last_poco_query" => array("type" => "datetime", "default" => NULL_DATE),
+					"last_contact" => array("type" => "datetime", "default" => NULL_DATE),
+					"last_failure" => array("type" => "datetime", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("id"),
@@ -956,7 +956,7 @@ function db_definition($charset) {
 					"duplex" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"note" => array("type" => "text"),
 					"hash" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"datetime" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"datetime" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"blocked" => array("type" => "tinyint(1)", "not null" => "1", "default" => "1"),
 					"ignore" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					),
@@ -979,11 +979,11 @@ function db_definition($charset) {
 					"parent-uri" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"extid" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"thr-parent" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"edited" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"commented" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"received" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"changed" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"edited" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"commented" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"received" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"changed" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"owner-id" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"owner-name" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"owner-link" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
@@ -1082,7 +1082,7 @@ function db_definition($charset) {
 					"id" => array("type" => "int(11)", "not null" => "1", "extra" => "auto_increment", "primary" => "1"),
 					"name" => array("type" => "varchar(128)", "not null" => "1", "default" => ""),
 					"locked" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
-					"created" => array("type" => "datetime", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("id"),
@@ -1106,7 +1106,7 @@ function db_definition($charset) {
 					"unknown" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"uri" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"parent-uri" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("id"),
@@ -1130,7 +1130,7 @@ function db_definition($charset) {
 					"action" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"movetofolder" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"pubmail" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
-					"last_check" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"last_check" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("id"),
@@ -1155,7 +1155,7 @@ function db_definition($charset) {
 					"name" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"url" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"photo" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"date" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"date" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"msg" => array("type" => "mediumtext"),
 					"uid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"link" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
@@ -1191,7 +1191,7 @@ function db_definition($charset) {
 			"fields" => array(
 					"url" => array("type" => "varbinary(255)", "not null" => "1", "primary" => "1"),
 					"content" => array("type" => "mediumtext"),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("url"),
@@ -1204,7 +1204,7 @@ function db_definition($charset) {
 					"guessing" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0", "primary" => "1"),
 					"oembed" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0", "primary" => "1"),
 					"content" => array("type" => "mediumtext"),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("url", "guessing", "oembed"),
@@ -1231,8 +1231,8 @@ function db_definition($charset) {
 					"contact-id" => array("type" => "int(10) unsigned", "not null" => "1", "default" => "0"),
 					"guid" => array("type" => "varchar(64)", "not null" => "1", "default" => ""),
 					"resource-id" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"edited" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"edited" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"title" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"desc" => array("type" => "text"),
 					"album" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
@@ -1294,7 +1294,7 @@ function db_definition($charset) {
 			"fields" => array(
 					"pid" => array("type" => "int(10) unsigned", "not null" => "1", "primary" => "1"),
 					"command" => array("type" => "varbinary(32)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("pid"),
@@ -1320,7 +1320,7 @@ function db_definition($charset) {
 					"gender" => array("type" => "varchar(32)", "not null" => "1", "default" => ""),
 					"marital" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"with" => array("type" => "text"),
-					"howlong" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"howlong" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"sexual" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"politic" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"religion" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
@@ -1372,7 +1372,7 @@ function db_definition($charset) {
 					"topic" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"nickname" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"push" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
-					"last_update" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"last_update" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"secret" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					),
 			"indexes" => array(
@@ -1384,8 +1384,8 @@ function db_definition($charset) {
 					"id" => array("type" => "int(11)", "not null" => "1", "extra" => "auto_increment", "primary" => "1"),
 					"cid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"network" => array("type" => "varchar(32)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"last" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"last" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"content" => array("type" => "mediumtext"),
 					"batch" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					),
@@ -1402,7 +1402,7 @@ function db_definition($charset) {
 			"fields" => array(
 					"id" => array("type" => "int(11) unsigned", "not null" => "1", "extra" => "auto_increment", "primary" => "1"),
 					"hash" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"uid" => array("type" => "int(11) unsigned", "not null" => "1", "default" => "0"),
 					"password" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"language" => array("type" => "varchar(16)", "not null" => "1", "default" => ""),
@@ -1456,7 +1456,7 @@ function db_definition($charset) {
 					"spam" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"ham" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"term" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"date" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"date" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("id"),
@@ -1475,8 +1475,8 @@ function db_definition($charset) {
 					"term" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"url" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"guid" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"received" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"received" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"global" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"aid" => array("type" => "int(10) unsigned", "not null" => "1", "default" => "0"),
 					"uid" => array("type" => "int(10) unsigned", "not null" => "1", "default" => "0"),
@@ -1497,11 +1497,11 @@ function db_definition($charset) {
 					"gcontact-id" => array("type" => "int(11) unsigned", "not null" => "1", "default" => "0"),
 					"owner-id" => array("type" => "int(11) unsigned", "not null" => "1", "default" => "0"),
 					"author-id" => array("type" => "int(11) unsigned", "not null" => "1", "default" => "0"),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"edited" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"commented" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"received" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"changed" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"edited" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"commented" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"received" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"changed" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"wall" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"private" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"pubmail" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
@@ -1552,8 +1552,8 @@ function db_definition($charset) {
 					"openid" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"timezone" => array("type" => "varchar(128)", "not null" => "1", "default" => ""),
 					"language" => array("type" => "varchar(32)", "not null" => "1", "default" => "en"),
-					"register_date" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"login_date" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"register_date" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"login_date" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"default-location" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
 					"allow_location" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"theme" => array("type" => "varchar(255)", "not null" => "1", "default" => ""),
@@ -1577,8 +1577,8 @@ function db_definition($charset) {
 					"expire" => array("type" => "int(11) unsigned", "not null" => "1", "default" => "0"),
 					"account_removed" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
 					"account_expired" => array("type" => "tinyint(1)", "not null" => "1", "default" => "0"),
-					"account_expires_on" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
-					"expire_notification_sent" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"account_expires_on" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
+					"expire_notification_sent" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"service_class" => array("type" => "varchar(32)", "not null" => "1", "default" => ""),
 					"def_gid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
 					"allow_cid" => array("type" => "mediumtext"),
@@ -1607,9 +1607,9 @@ function db_definition($charset) {
 					"id" => array("type" => "int(11)", "not null" => "1", "extra" => "auto_increment", "primary" => "1"),
 					"parameter" => array("type" => "text"),
 					"priority" => array("type" => "tinyint(3) unsigned", "not null" => "1", "default" => "0"),
-					"created" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"created" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					"pid" => array("type" => "int(11)", "not null" => "1", "default" => "0"),
-					"executed" => array("type" => "datetime", "not null" => "1", "default" => "0000-00-00 00:00:00"),
+					"executed" => array("type" => "datetime", "not null" => "1", "default" => NULL_DATE),
 					),
 			"indexes" => array(
 					"PRIMARY" => array("id"),
diff --git a/include/diaspora.php b/include/diaspora.php
index eca22092d8..302492efea 100644
--- a/include/diaspora.php
+++ b/include/diaspora.php
@@ -3574,7 +3574,7 @@ class Diaspora {
 		if ($searchable === 'true') {
 			$dob = '1000-00-00';
 
-			if (($profile['dob']) && ($profile['dob'] != '0000-00-00'))
+			if (($profile['dob']) && ($profile['dob'] > '0001-01-01'))
 				$dob = ((intval($profile['dob'])) ? intval($profile['dob']) : '1000') .'-'. datetime_convert('UTC','UTC',$profile['dob'],'m-d');
 
 			$about = $profile['about'];
diff --git a/include/identity.php b/include/identity.php
index ab80c71cea..670337e087 100644
--- a/include/identity.php
+++ b/include/identity.php
@@ -628,7 +628,7 @@ function advanced_profile(App $a) {
 		if($a->profile['gender']) $profile['gender'] = array( t('Gender:'),  $a->profile['gender'] );
 
 
-		if(($a->profile['dob']) && ($a->profile['dob'] != '0000-00-00')) {
+		if(($a->profile['dob']) && ($a->profile['dob'] > '0001-01-01')) {
 
 			$year_bd_format = t('j F, Y');
 			$short_bd_format = t('j F');
@@ -652,7 +652,7 @@ function advanced_profile(App $a) {
 			$profile['marital']['with'] = $a->profile['with'];
 		}
 
-		if (strlen($a->profile['howlong']) && $a->profile['howlong'] !== '0000-00-00 00:00:00') {
+		if (strlen($a->profile['howlong']) && $a->profile['howlong'] >= NULL_DATE) {
 			$profile['howlong'] = relative_date($a->profile['howlong'], t('for %1$d %2$s'));
 		}
 
diff --git a/include/lock.php b/include/lock.php
index b3d488a357..a48b0ad342 100644
--- a/include/lock.php
+++ b/include/lock.php
@@ -68,7 +68,8 @@ function block_on_function_lock($fn_name, $wait_sec = 2, $timeout = 30) {
 
 if(! function_exists('unlock_function')) {
 function unlock_function($fn_name) {
-	$r = q("UPDATE `locks` SET `locked` = 0, `created` = '0000-00-00 00:00:00' WHERE `name` = '%s'",
+	$r = q("UPDATE `locks` SET `locked` = 0, `created` = '%s' WHERE `name` = '%s'",
+			dbesc(NULL_DATE),
 			dbesc($fn_name)
 	     );
 
diff --git a/include/onepoll.php b/include/onepoll.php
index 5219d9f3bd..90ca639dd1 100644
--- a/include/onepoll.php
+++ b/include/onepoll.php
@@ -152,7 +152,7 @@ function onepoll_run(&$argv, &$argc){
 
 	logger("onepoll: poll: ({$contact['id']}) IMPORTER: {$importer['name']}, CONTACT: {$contact['name']}");
 
-	$last_update = (($contact['last-update'] === '0000-00-00 00:00:00')
+	$last_update = (($contact['last-update'] <= NULL_DATE)
 		? datetime_convert('UTC','UTC','now - 7 days', ATOM_TIME)
 		: datetime_convert('UTC','UTC',$contact['last-update'], ATOM_TIME)
 	);
@@ -250,7 +250,7 @@ function onepoll_run(&$argv, &$argc){
 			mark_for_death($contact);
 		}
 		else {
-			if($contact['term-date'] != '0000-00-00 00:00:00') {
+			if ($contact['term-date'] > NULL_DATE) {
 				logger("poller: $url back from the dead - removing mark for death");
 				unmark_for_death($contact);
 			}
diff --git a/include/poller.php b/include/poller.php
index 8be4c1835c..a82d265880 100644
--- a/include/poller.php
+++ b/include/poller.php
@@ -343,7 +343,7 @@ function poller_max_connections_reached() {
  *
  */
 function poller_kill_stale_workers() {
-	$r = q("SELECT `pid`, `executed`, `priority`, `parameter` FROM `workerqueue` WHERE `executed` != '0000-00-00 00:00:00'");
+	$r = q("SELECT `pid`, `executed`, `priority`, `parameter` FROM `workerqueue` WHERE `executed` > '%s'", dbesc(NULL_DATE));
 
 	if (!dbm::is_result($r)) {
 		// No processing here needed
@@ -352,8 +352,8 @@ function poller_kill_stale_workers() {
 
 	foreach($r AS $pid)
 		if (!posix_kill($pid["pid"], 0))
-			q("UPDATE `workerqueue` SET `executed` = '0000-00-00 00:00:00', `pid` = 0 WHERE `pid` = %d",
-				intval($pid["pid"]));
+			q("UPDATE `workerqueue` SET `executed` = '%s', `pid` = 0 WHERE `pid` = %d",
+				dbesc(NULL_DATE), intval($pid["pid"]));
 		else {
 			// Kill long running processes
 
@@ -377,8 +377,9 @@ function poller_kill_stale_workers() {
 				// We killed the stale process.
 				// To avoid a blocking situation we reschedule the process at the beginning of the queue.
 				// Additionally we are lowering the priority.
-				q("UPDATE `workerqueue` SET `executed` = '0000-00-00 00:00:00', `created` = '%s',
+				q("UPDATE `workerqueue` SET `executed` = '%s', `created` = '%s',
 							`priority` = %d, `pid` = 0 WHERE `pid` = %d",
+					dbesc(NULL_DATE),
 					dbesc(datetime_convert()),
 					intval(PRIORITY_NEGLIGIBLE),
 					intval($pid["pid"]));
@@ -411,15 +412,15 @@ function poller_too_much_workers() {
 		$slope = $maxworkers / pow($maxsysload, $exponent);
 		$queues = ceil($slope * pow(max(0, $maxsysload - $load), $exponent));
 
-		$s = q("SELECT COUNT(*) AS `total` FROM `workerqueue` WHERE `executed` = '0000-00-00 00:00:00'");
+		$s = q("SELECT COUNT(*) AS `total` FROM `workerqueue` WHERE `executed` <= '%s'", dbesc(NULL_DATE));
 		$entries = $s[0]["total"];
 
 		if (Config::get("system", "worker_fastlane", false) AND ($queues > 0) AND ($entries > 0) AND ($active >= $queues)) {
-			$s = q("SELECT `priority` FROM `workerqueue` WHERE `executed` = '0000-00-00 00:00:00' ORDER BY `priority` LIMIT 1");
+			$s = q("SELECT `priority` FROM `workerqueue` WHERE `executed` <= '%s' ORDER BY `priority` LIMIT 1", dbesc(NULL_DATE));
 			$top_priority = $s[0]["priority"];
 
-			$s = q("SELECT `id` FROM `workerqueue` WHERE `priority` <= %d AND `executed` != '0000-00-00 00:00:00' LIMIT 1",
-				intval($top_priority));
+			$s = q("SELECT `id` FROM `workerqueue` WHERE `priority` <= %d AND `executed` > '%s' LIMIT 1",
+				intval($top_priority), dbesc(NULL_DATE));
 			$high_running = dbm::is_result($s);
 
 			if (!$high_running AND ($top_priority > PRIORITY_UNDEFINED) AND ($top_priority < PRIORITY_NEGLIGIBLE)) {
@@ -539,20 +540,24 @@ function poller_worker_process() {
 	if (poller_passing_slow($highest_priority)) {
 		// Are there waiting processes with a higher priority than the currently highest?
 		$r = q("SELECT * FROM `workerqueue`
-				WHERE `executed` = '0000-00-00 00:00:00' AND `priority` < %d
-				ORDER BY `priority`, `created` LIMIT 1", dbesc($highest_priority));
+				WHERE `executed` <= '%s' AND `priority` < %d
+				ORDER BY `priority`, `created` LIMIT 1",
+				dbesc(NULL_DATE),
+				intval($highest_priority));
 		if (dbm::is_result($r))
 			return $r;
 
 		// Give slower processes some processing time
 		$r = q("SELECT * FROM `workerqueue`
-				WHERE `executed` = '0000-00-00 00:00:00' AND `priority` > %d
-				ORDER BY `priority`, `created` LIMIT 1", dbesc($highest_priority));
+				WHERE `executed` <= '%s' AND `priority` > %d
+				ORDER BY `priority`, `created` LIMIT 1",
+				dbesc(NULL_DATE),
+				intval($highest_priority));
 	}
 
 	// If there is no result (or we shouldn't pass lower processes) we check without priority limit
 	if (($highest_priority == 0) OR !dbm::is_result($r))
-		$r = q("SELECT * FROM `workerqueue` WHERE `executed` = '0000-00-00 00:00:00' ORDER BY `priority`, `created` LIMIT 1");
+		$r = q("SELECT * FROM `workerqueue` WHERE `executed` <= '%s' ORDER BY `priority`, `created` LIMIT 1", dbesc(NULL_DATE));
 
 	return $r;
 }
diff --git a/include/security.php b/include/security.php
index c379518562..11a2955b4c 100644
--- a/include/security.php
+++ b/include/security.php
@@ -16,7 +16,7 @@ function authenticate_success($user_record, $login_initial = false, $interactive
 	$a->user = $user_record;
 
 	if($interactive) {
-		if($a->user['login_date'] === '0000-00-00 00:00:00') {
+		if($a->user['login_date'] <= NULL_DATE) {
 			$_SESSION['return_url'] = 'profile_photo/new';
 			$a->module = 'profile_photo';
 			info( t("Welcome ") . $a->user['username'] . EOL);
diff --git a/include/socgraph.php b/include/socgraph.php
index a0dd88df2d..0421f3f219 100644
--- a/include/socgraph.php
+++ b/include/socgraph.php
@@ -81,7 +81,7 @@ function poco_load($cid,$uid = 0,$zcid = 0,$url = null) {
 		$connect_url = '';
 		$name = '';
 		$network = '';
-		$updated = '0000-00-00 00:00:00';
+		$updated = NULL_DATE;
 		$location = '';
 		$about = '';
 		$keywords = '';
@@ -242,7 +242,7 @@ function poco_check($profile_url, $name, $network, $profile_photo, $about, $loca
 		if (($network == "") AND ($x[0]["network"] != NETWORK_STATUSNET))
 			$network = $x[0]["network"];
 
-		if ($updated == "0000-00-00 00:00:00")
+		if ($updated <= NULL_DATE)
 			$updated = $x[0]["updated"];
 
 		$created = $x[0]["created"];
@@ -252,7 +252,7 @@ function poco_check($profile_url, $name, $network, $profile_photo, $about, $loca
 		$alias =  $x[0]["alias"];
 		$notify =  $x[0]["notify"];
 	} else {
-		$created = "0000-00-00 00:00:00";
+		$created = NULL_DATE;
 		$server_url = "";
 
 		$urlparts = parse_url($profile_url);
@@ -420,7 +420,7 @@ function poco_last_updated($profile, $force = false) {
 	$gcontacts = q("SELECT * FROM `gcontact` WHERE `nurl` = '%s'",
 			dbesc(normalise_link($profile)));
 
-	if ($gcontacts[0]["created"] == "0000-00-00 00:00:00")
+	if ($gcontacts[0]["created"] <= NULL_DATE)
 		q("UPDATE `gcontact` SET `created` = '%s' WHERE `nurl` = '%s'",
 			dbesc(datetime_convert()), dbesc(normalise_link($profile)));
 
@@ -619,7 +619,7 @@ function poco_last_updated($profile, $force = false) {
 	// Maybe there aren't any entries. Then check if it is a valid feed
 	if ($last_updated == "")
 		if ($xpath->query('/atom:feed')->length > 0)
-			$last_updated = "0000-00-00 00:00:00";
+			$last_updated = NULL_DATE;
 
 	q("UPDATE `gcontact` SET `updated` = '%s', `last_contact` = '%s' WHERE `nurl` = '%s'",
 		dbesc(dbm::date($last_updated)), dbesc(dbm::date()), dbesc(normalise_link($profile)));
@@ -692,7 +692,7 @@ function poco_check_server($server_url, $network = "", $force = false) {
 	$servers = q("SELECT * FROM `gserver` WHERE `nurl` = '%s'", dbesc(normalise_link($server_url)));
 	if ($servers) {
 
-		if ($servers[0]["created"] == "0000-00-00 00:00:00")
+		if ($servers[0]["created"] <= NULL_DATE)
 			q("UPDATE `gserver` SET `created` = '%s' WHERE `nurl` = '%s'",
 				dbesc(datetime_convert()), dbesc(normalise_link($server_url)));
 
@@ -723,8 +723,8 @@ function poco_check_server($server_url, $network = "", $force = false) {
 		$info = "";
 		$register_policy = -1;
 
-		$last_contact = "0000-00-00 00:00:00";
-		$last_failure = "0000-00-00 00:00:00";
+		$last_contact = NULL_DATE;
+		$last_failure = NULL_DATE;
 	}
 	logger("Server ".$server_url." is outdated or unknown. Start discovery. Force: ".$force." Created: ".$servers[0]["created"]." Failure: ".$last_failure." Contact: ".$last_contact, LOGGER_DEBUG);
 
@@ -1128,7 +1128,7 @@ function suggestion_query($uid, $start = 0, $limit = 80) {
 		where uid = %d and not gcontact.nurl in ( select nurl from contact where uid = %d )
 		AND NOT `gcontact`.`name` IN (SELECT `name` FROM `contact` WHERE `uid` = %d)
 		AND NOT `gcontact`.`id` IN (SELECT `gcid` FROM `gcign` WHERE `uid` = %d)
-		AND `gcontact`.`updated` != '0000-00-00 00:00:00'
+		AND `gcontact`.`updated` >= '%s'
 		AND `gcontact`.`last_contact` >= `gcontact`.`last_failure`
 		AND `gcontact`.`network` IN (%s)
 		GROUP BY `glink`.`gcid` ORDER BY `gcontact`.`updated` DESC,`total` DESC LIMIT %d, %d",
@@ -1136,6 +1136,7 @@ function suggestion_query($uid, $start = 0, $limit = 80) {
 		intval($uid),
 		intval($uid),
 		intval($uid),
+		dbesc(NULL_DATE),
 		$sql_network,
 		intval($start),
 		intval($limit)
@@ -1154,13 +1155,14 @@ function suggestion_query($uid, $start = 0, $limit = 80) {
 		WHERE `glink`.`uid` = 0 AND `glink`.`cid` = 0 AND `glink`.`zcid` = 0 AND NOT `gcontact`.`nurl` IN (SELECT `nurl` FROM `contact` WHERE `uid` = %d)
 		AND NOT `gcontact`.`name` IN (SELECT `name` FROM `contact` WHERE `uid` = %d)
 		AND NOT `gcontact`.`id` IN (SELECT `gcid` FROM `gcign` WHERE `uid` = %d)
-		AND `gcontact`.`updated` != '0000-00-00 00:00:00'
+		AND `gcontact`.`updated` >= '%s'
 		AND `gcontact`.`last_contact` >= `gcontact`.`last_failure`
 		AND `gcontact`.`network` IN (%s)
 		ORDER BY rand() LIMIT %d, %d",
 		intval($uid),
 		intval($uid),
 		intval($uid),
+		dbesc(NULL_DATE),
 		$sql_network,
 		intval($start),
 		intval($limit)
@@ -1374,7 +1376,7 @@ function poco_discover_server($data, $default_generation = 0) {
 		$connect_url = '';
 		$name = '';
 		$network = '';
-		$updated = '0000-00-00 00:00:00';
+		$updated = NULL_DATE;
 		$location = '';
 		$about = '';
 		$keywords = '';
diff --git a/include/uimport.php b/include/uimport.php
index b774d78c6d..c6eeb6fc73 100644
--- a/include/uimport.php
+++ b/include/uimport.php
@@ -186,8 +186,8 @@ function import_account(App $a, $file) {
 			}
 		}
 		if ($contact['uid'] == $olduid && $contact['self'] == '0') {
-			// set contacts 'avatar-date' to "0000-00-00 00:00:00" to let poller to update urls
-			$contact["avatar-date"] = "0000-00-00 00:00:00" ;
+			// set contacts 'avatar-date' to NULL_DATE to let poller to update urls
+			$contact["avatar-date"] = NULL_DATE;
 
 
 			switch ($contact['network']) {
diff --git a/library/Smarty/libs/plugins/modifier.date_format.php b/library/Smarty/libs/plugins/modifier.date_format.php
index 5ad7540b15..c5992991de 100644
--- a/library/Smarty/libs/plugins/modifier.date_format.php
+++ b/library/Smarty/libs/plugins/modifier.date_format.php
@@ -36,7 +36,7 @@ function smarty_modifier_date_format($string, $format = null, $default_date = ''
      * Include the {@link shared.make_timestamp.php} plugin
      */
     require_once(SMARTY_PLUGINS_DIR . 'shared.make_timestamp.php');
-    if ($string != '' && $string != '0000-00-00' && $string != '0000-00-00 00:00:00') {
+    if ($string != '' && $string > '0001-01-01' && $string > NULL_DATE) {
         $timestamp = smarty_make_timestamp($string);
     } elseif ($default_date != '') {
         $timestamp = smarty_make_timestamp($default_date);
diff --git a/mod/contacts.php b/mod/contacts.php
index a2a77e2a5c..5fdcb7036d 100644
--- a/mod/contacts.php
+++ b/mod/contacts.php
@@ -534,11 +534,11 @@ function contacts_content(App $a) {
 
 		$insecure = t('Private communications are not available for this contact.');
 
-		$last_update = (($contact['last-update'] == '0000-00-00 00:00:00')
+		$last_update = (($contact['last-update'] <= NULL_DATE)
 				? t('Never')
 				: datetime_convert('UTC',date_default_timezone_get(),$contact['last-update'],'D, j M Y, g:i A'));
 
-		if($contact['last-update'] !== '0000-00-00 00:00:00')
+		if($contact['last-update'] > NULL_DATE)
 			$last_update .= ' ' . (($contact['last-update'] <= $contact['success_update']) ? t("\x28Update was successful\x29") : t("\x28Update was not successful\x29"));
 
 		$lblsuggest = (($contact['network'] === NETWORK_DFRN) ? t('Suggest friends') : '');
@@ -558,7 +558,7 @@ function contacts_content(App $a) {
 		// tabs
 		$tab_str = contacts_tab($a, $contact_id, 2);
 
-		$lost_contact = (($contact['archive'] && $contact['term-date'] != '0000-00-00 00:00:00' && $contact['term-date'] < datetime_convert('','','now')) ? t('Communications lost with this contact!') : '');
+		$lost_contact = (($contact['archive'] && $contact['term-date'] > NULL_DATE && $contact['term-date'] < datetime_convert('','','now')) ? t('Communications lost with this contact!') : '');
 
 		if ($contact['network'] == NETWORK_FEED)
 			$fetch_further_information = array('fetch_further_information', t('Fetch further information for feeds'), $contact['fetch_further_information'], t('Fetch further information for feeds'),
diff --git a/mod/events.php b/mod/events.php
index ac0c444cb5..2b84d903e1 100644
--- a/mod/events.php
+++ b/mod/events.php
@@ -60,7 +60,7 @@ function events_post(App $a) {
 	}
 
 	if ($nofinish) {
-		$finish = '0000-00-00 00:00:00';
+		$finish = NULL_DATE;
 	}
 
 	if ($finish_text) {
diff --git a/mod/hovercard.php b/mod/hovercard.php
index ec749db208..ea1036b898 100644
--- a/mod/hovercard.php
+++ b/mod/hovercard.php
@@ -75,7 +75,7 @@ function hovercard_content() {
 		'tags' => $contact["keywords"],
 //		'nsfw' => intval($contact["nsfw"]),
 //		'server_url' => $contact["server_url"],
-		'bd' => (($contact["birthday"] == "0000-00-00") ? "" : $contact["birthday"]),
+		'bd' => (($contact["birthday"] <= "0001-01-01") ? "" : $contact["birthday"]),
 //		'generation' => $contact["generation"],
 		'account_type' => account_type($contact),
 		'actions' => $actions,
diff --git a/mod/profiles.php b/mod/profiles.php
index 4c6ff926b6..4ec4538389 100644
--- a/mod/profiles.php
+++ b/mod/profiles.php
@@ -191,21 +191,21 @@ function profiles_post(App $a) {
 			return;
 		}
 
-		$dob = $_POST['dob'] ? escape_tags(trim($_POST['dob'])) : '0000-00-00'; // FIXME: Needs to be validated?
+		$dob = $_POST['dob'] ? escape_tags(trim($_POST['dob'])) : '0001-01-01'; // FIXME: Needs to be validated?
 
 		$y = substr($dob,0,4);
 		if((! ctype_digit($y)) || ($y < 1900))
 			$ignore_year = true;
 		else
 			$ignore_year = false;
-		if($dob != '0000-00-00') {
-			if(strpos($dob,'0000-') === 0) {
+		if($dob > '0001-01-01') {
+			if(strpos($dob,'000') === 0) {
 				$ignore_year = true;
 				$dob = substr($dob,5);
 			}
 			$dob = datetime_convert('UTC','UTC',(($ignore_year) ? '1900-' . $dob : $dob),(($ignore_year) ? 'm-d' : 'Y-m-d'));
 			if($ignore_year)
-				$dob = '0000-' . $dob;
+				$dob = '0001-' . $dob;
 		}
 
 		$name = notags(trim($_POST['name']));
@@ -234,7 +234,7 @@ function profiles_post(App $a) {
 		$with = ((x($_POST,'with')) ? notags(trim($_POST['with'])) : '');
 
 		if(! strlen($howlong))
-			$howlong = '0000-00-00 00:00:00';
+			$howlong = NULL_DATE;
 		else
 			$howlong = datetime_convert(date_default_timezone_get(),'UTC',$howlong);
 
@@ -721,7 +721,7 @@ function profiles_content(App $a) {
 			'$gender' => gender_selector($r[0]['gender']),
 			'$marital' => marital_selector($r[0]['marital']),
 			'$with' => array('with', t("Who: \x28if applicable\x29"), strip_tags($r[0]['with']), t('Examples: cathy123, Cathy Williams, cathy@example.com')),
-			'$howlong' => array('howlong', t('Since [date]:'), ($r[0]['howlong'] === '0000-00-00 00:00:00' ? '' : datetime_convert('UTC',date_default_timezone_get(),$r[0]['howlong']))),
+			'$howlong' => array('howlong', t('Since [date]:'), ($r[0]['howlong'] <= NULL_DATE ? '' : datetime_convert('UTC',date_default_timezone_get(),$r[0]['howlong']))),
 			'$sexual' => sexpref_selector($r[0]['sexual']),
 			'$about' => array('about', t('Tell us about yourself...'), $r[0]['about']),
 			'$xmpp' => array('xmpp', t('XMPP (Jabber) address:'), $r[0]['xmpp'], t("The XMPP address will be propagated to your contacts so that they can follow you.")),
diff --git a/mod/settings.php b/mod/settings.php
index 32ccaf541a..5c9c439e0a 100644
--- a/mod/settings.php
+++ b/mod/settings.php
@@ -872,7 +872,7 @@ function settings_content(App $a) {
 		$mail_pubmail      = ((dbm::is_result($r)) ? $r[0]['pubmail'] : 0);
 		$mail_action       = ((dbm::is_result($r)) ? $r[0]['action'] : 0);
 		$mail_movetofolder = ((dbm::is_result($r)) ? $r[0]['movetofolder'] : '');
-		$mail_chk          = ((dbm::is_result($r)) ? $r[0]['last_check'] : '0000-00-00 00:00:00');
+		$mail_chk          = ((dbm::is_result($r)) ? $r[0]['last_check'] : NULL_DATE);
 
 
 		$tpl = get_markup_template("settings_connectors.tpl");
diff --git a/update.php b/update.php
index 041de9cfff..1696bb3a04 100644
--- a/update.php
+++ b/update.php
@@ -48,8 +48,8 @@ function update_1000() {
 
 	q("ALTER TABLE `intro` ADD `duplex` TINYINT( 1 ) NOT NULL DEFAULT '0' AFTER `knowyou` ");
 	q("ALTER TABLE `contact` ADD `duplex` TINYINT( 1 ) NOT NULL DEFAULT '0' AFTER `rel` ");
- 	q("ALTER TABLE `contact` CHANGE `issued-pubkey` `issued-pubkey` TEXT CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL");
-	q("ALTER TABLE `contact` ADD `term-date` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00' AFTER `avatar-date`");
+ 	q("ALTER TABLE `contact` CHANGE `issued-pubkey` `issued-pubkey` TEXTCHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL");
+	q("ALTER TABLE `contact` ADD `term-date` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00' AFTER `avatar-date`");
 }
 
 function update_1001() {
@@ -242,8 +242,8 @@ function update_1022() {
 }
 
 function update_1023() {
-	q("ALTER TABLE `user` ADD `register_date` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00' AFTER `timezone` ,
-	ADD `login_date` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00' AFTER `register_date` ");
+	q("ALTER TABLE `user` ADD `register_date` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00' AFTER `timezone` ,
+	ADD `login_date` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00' AFTER `register_date` ");
 }
 
 function update_1024() {
@@ -349,7 +349,7 @@ function update_1034() {
 
 function update_1035() {
 
-	q("ALTER TABLE `contact` ADD `success_update` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00' AFTER `last-update` ");
+	q("ALTER TABLE `contact` ADD `success_update` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00' AFTER `last-update` ");
 
 }
 
@@ -443,7 +443,7 @@ function update_1049() {
 	`user` CHAR( 255 ) NOT NULL ,
 	`pass` CHAR( 255 ) NOT NULL ,
 	`reply_to` CHAR( 255 ) NOT NULL ,
-	`last_check` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00'
+	`last_check` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00'
 	) ENGINE = MYISAM ");
 }
 
@@ -454,8 +454,8 @@ function update_1050() {
 	`filetype` CHAR( 64 ) NOT NULL ,
 	`filesize` INT NOT NULL ,
 	`data` LONGBLOB NOT NULL ,
-	`created` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00',
-	`edited` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00',
+	`created` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00',
+	`edited` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00',
 	`allow_cid` MEDIUMTEXT NOT NULL ,
 	`allow_gid` MEDIUMTEXT NOT NULL ,
 	`deny_cid` MEDIUMTEXT NOT NULL ,
@@ -531,7 +531,7 @@ function update_1065() {
 }
 
 function update_1066() {
-	$r = q("ALTER TABLE `item` ADD `received` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00' AFTER `edited` ");
+	$r = q("ALTER TABLE `item` ADD `received` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00' AFTER `edited` ");
 	if($r)
 		q("ALTER TABLE `item` ADD INDEX ( `received` ) ");
 
@@ -673,7 +673,7 @@ function update_1079() {
 }
 
 function update_1080() {
-	q("ALTER TABLE `fcontact` ADD `updated` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00'");
+	q("ALTER TABLE `fcontact` ADD `updated` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00'");
 }
 
 function update_1081() {
@@ -728,7 +728,7 @@ function update_1086() {
 }
 
 function update_1087() {
-	q("ALTER TABLE `item` ADD `commented` datetime NOT NULL DEFAULT '0000-00-00 00:00:00' AFTER `edited` ");
+	q("ALTER TABLE `item` ADD `commented` datetime NOT NULL DEFAULT '0001-01-01 00:00:00' AFTER `edited` ");
 
 	$r = q("SELECT `id` FROM `item` WHERE `parent` = `id` ");
 	if (dbm::is_result($r)) {
@@ -747,8 +747,8 @@ function update_1087() {
 
 function update_1088() {
 	q("ALTER TABLE `user` ADD `account_expired` TINYINT( 1 ) NOT NULL DEFAULT '0' AFTER `expire` ,
-		ADD `account_expires_on` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00' AFTER `account_expired` ,
-		ADD `expire_notification_sent` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00' AFTER `account_expires_on` ");
+		ADD `account_expires_on` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00' AFTER `account_expired` ,
+		ADD `expire_notification_sent` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00' AFTER `account_expires_on` ");
 }
 
 function update_1089() {
@@ -932,8 +932,8 @@ ADD INDEX ( `hidden` ) ");
 
 function update_1109() {
 	q("ALTER TABLE `conv` ADD `creator` CHAR( 255 ) NOT NULL ,
-		ADD `created` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00',
-		ADD `updated` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00',
+		ADD `created` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00',
+		ADD `updated` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00',
 		ADD `subject` MEDIUMTEXT NOT NULL,
 		ADD INDEX ( `created` ), ADD INDEX ( `updated` ) ");
 }
@@ -1112,7 +1112,7 @@ function update_1127() {
 
 
 function update_1128() {
-	q("alter table spam add `date` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00' AFTER `term` ");
+	q("alter table spam add `date` DATETIME NOT NULL DEFAULT '0001-01-01 00:00:00' AFTER `term` ");
 }
 
 function update_1129() {
@@ -1262,7 +1262,7 @@ function update_1144() {
 }
 
 function update_1145() {
-	$r = q("alter table profile add howlong datetime not null default '0000-00-00 00:00:00' after `with`");
+	$r = q("alter table profile add howlong datetime not null default '0001-01-01 00:00:00' after `with`");
 	if(! $r)
 		return UPDATE_FAILED ;
 	return UPDATE_SUCCESS ;
@@ -1562,11 +1562,11 @@ function update_1169() {
 		  `iid` int(10) unsigned NOT NULL DEFAULT '0',
 		  `uid` int(10) unsigned NOT NULL DEFAULT '0',
 		  `contact-id` int(11) unsigned NOT NULL DEFAULT '0',
-		  `created` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
-		  `edited` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
-		  `commented` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
-		  `received` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
-		  `changed` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
+		  `created` datetime NOT NULL DEFAULT '0001-01-01 00:00:00',
+		  `edited` datetime NOT NULL DEFAULT '0001-01-01 00:00:00',
+		  `commented` datetime NOT NULL DEFAULT '0001-01-01 00:00:00',
+		  `received` datetime NOT NULL DEFAULT '0001-01-01 00:00:00',
+		  `changed` datetime NOT NULL DEFAULT '0001-01-01 00:00:00',
 		  `wall` tinyint(1) NOT NULL DEFAULT '0',
 		  `private` tinyint(1) NOT NULL DEFAULT '0',
 		  `pubmail` tinyint(1) NOT NULL DEFAULT '0',