diff --git a/include/datetime.php b/include/datetime.php
index 601b4decf..fd60f5fd9 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($s,0,10) <= '0001-01-01') {
+	if(substr($s,0,10) == '0000-00-00') {
 		$d = new DateTime($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 <= '0001-01-01')
+	if($dob == '0000-00-00')
 		$value = '';
 	else
 		$value = (($year) ? datetime_convert('UTC','UTC',$dob,'Y-m-d') : datetime_convert('UTC','UTC',$dob,'m-d'));
@@ -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` >= '0001-01-01' AND SUBSTRING(`bd`,1,4) != `bdyear` ");
+	$r = q("SELECT * FROM contact WHERE `bd` != '' AND `bd` != '0000-00-00' AND SUBSTRING(`bd`,1,4) != `bdyear` ");
 	if (dbm::is_result($r)) {
 		foreach ($r as $rr) {
 
diff --git a/include/dfrn.php b/include/dfrn.php
index 39372aef1..de64c37d6 100644
--- a/include/dfrn.php
+++ b/include/dfrn.php
@@ -1094,7 +1094,7 @@ class dfrn {
 			return 3;
 		}
 
-		if($contact['term-date'] != '0000-00-00 00:00:00') {
+		if($contact['term-date'] > NULL_DATE) {
 			logger("dfrn_deliver: $url back from the dead - removing mark for death");
 			require_once('include/Contact.php');
 			unmark_for_death($contact);
diff --git a/include/diaspora.php b/include/diaspora.php
index 302492efe..eca22092d 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'] > '0001-01-01'))
+			if (($profile['dob']) && ($profile['dob'] != '0000-00-00'))
 				$dob = ((intval($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 670337e08..8138e9b04 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'] > '0001-01-01')) {
+		if(($a->profile['dob']) && ($a->profile['dob'] != '0000-00-00')) {
 
 			$year_bd_format = t('j F, Y');
 			$short_bd_format = t('j F');
diff --git a/mod/profiles.php b/mod/profiles.php
index 4ec453838..bf6e828b6 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'])) : '0001-01-01'; // FIXME: Needs to be validated?
+		$dob = $_POST['dob'] ? escape_tags(trim($_POST['dob'])) : '0000-00-00'; // 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 > '0001-01-01') {
-			if(strpos($dob,'000') === 0) {
+		if($dob != '0000-00-00') {
+			if(strpos($dob,'0000-') === 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 = '0001-' . $dob;
+				$dob = '0000-' . $dob;
 		}
 
 		$name = notags(trim($_POST['name']));