Index: Gruntfile.js
===================================================================
--- Gruntfile.js	(revision 28601)
+++ Gruntfile.js	(working copy)
@@ -79,7 +79,14 @@
 			version: {
 				options: {
 					processContent: function( src ) {
-						return src.replace( /^(\$wp_version.+?)-src';/m, '$1\';' );
+						return src.replace( /^\$wp_version = '(.+?)';/m, function( str, version ) {
+							version = version.replace( /-src$/, '' );
+
+							// If the version includes a date string (-yyyymmdd), update it.
+							version = version.replace( /-[\d]{8}$/, '-' + grunt.template.today( 'yyyymmdd' ) );
+
+							return "$wp_version = '" + version + "';";
+						});
 					}
 				},
 				src: SOURCE_DIR + 'wp-includes/version.php',