Index: Gruntfile.js
===================================================================
--- Gruntfile.js	(revision 26929)
+++ Gruntfile.js	(working copy)
@@ -43,7 +43,25 @@
 			version: {
 				options: {
 					processContent: function( src ) {
-						return src.replace( /^(\$wp_version.+?)-src';/m, '$1\';' );
+						return src.replace( /^\$wp_version = '(.+?)';/m, function( str, version ) {
+						    var date = new Date();
+
+							function zero( number ) {
+							    if ( number < 10 ) {
+							        return '0' + number;
+							    }
+							    return '' + number;
+							}
+
+							version = version.replace( '-src', '' );
+
+							if ( /[^0-9.]+/.test( version ) ) {
+								// If the version is alpha|beta|RC
+								version += '-' + date.getFullYear() + zero( date.getMonth() + 1 ) + zero( date.getDate() );
+							}
+
+							return "$wp_version = '" + version + "';";
+						});
 					}
 				},
 				files: [