diff --git a/config/mozBDate.pm b/config/mozBDate.pm
index 5bdd36ac19a..1b367e16738 100755
--- a/config/mozBDate.pm
+++ b/config/mozBDate.pm
@@ -46,14 +46,23 @@ sub write_number($) {
 sub UpdateBuildNumber($$) {
 
     my ($outfile, $official) = @_;
+    my $given_date = $ENV{"MOZ_BUILD_DATE"};
+    my $build_number;
 
-    # XP way of doing the build date.
-    # 1998091509 = 1998, September, 15th, 9am local time zone
-    my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime;
+    if ($given_date eq "") {
+	# XP way of doing the build date.
+	# 1998091509 = 1998, September, 15th, 9am local time zone
+	my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
+	    localtime(time);
 
-    # localtime returns year minus 1900
-    $year = $year + 1900;
-    my $build_number = sprintf("%04d%02d%02d%02d", $year, 1+$mon, $mday, $hour);
+	# localtime returns year minus 1900
+	$year = $year + 1900;
+	$build_number = sprintf("%04d%02d%02d%02d", $year, 1+$mon,
+				$mday, $hour);
+    }
+    else {
+	$build_number = $given_date;
+    }
 
     if ("$outfile" eq "") {
         print "$build_number\n";
diff --git a/content/build/gbdate.pl b/content/build/gbdate.pl
index abba8b57b0a..e69de29bb2d 100755
--- a/content/build/gbdate.pl
+++ b/content/build/gbdate.pl
@@ -1,27 +0,0 @@
-#
-# The contents of this file are subject to the Netscape Public
-# License Version 1.1 (the "License"); you may not use this file
-# except in compliance with the License. You may obtain a copy of
-# the License at http://www.mozilla.org/NPL/
-#
-# Software distributed under the License is distributed on an "AS
-# IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
-# implied. See the License for the specific language governing
-# rights and limitations under the License.
-#
-# The Original Code is mozilla.org code.
-#
-# The Initial Developer of the Original Code is Netscape
-# Communications Corporation.  Portions created by Netscape are
-# Copyright (C) 1998 Netscape Communications Corporation. All
-# Rights Reserved.
-#
-# Contributor(s): 
-#
-
-# XP way of doing the build date.
-# 1998091509 = 1998, September, 15th, 9am local time zone
-($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime;
-# localtime returns year minus 1900
-$year = $year + 1900;
-printf("#define PRODUCT_VERSION \"%04d%02d%02d\"\n", $year, 1+$mon, $mday);
diff --git a/layout/build/gbdate.pl b/layout/build/gbdate.pl
index abba8b57b0a..1b261936b60 100755
--- a/layout/build/gbdate.pl
+++ b/layout/build/gbdate.pl
@@ -19,6 +19,16 @@
 # Contributor(s): 
 #
 
+$given_date = $ENV{"MOZ_BUILD_DATE"};
+
+if ($given_date ne "") {
+	# The gecko date does not use hour resolution
+	chop($given_date);
+	chop($given_date);
+	printf("#define PRODUCT_VERSION \"%08d\"\n", $given_date);
+	exit(0);
+}
+
 # XP way of doing the build date.
 # 1998091509 = 1998, September, 15th, 9am local time zone
 ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime;