Switch substr to slice as IE8 doesn't do negative substr properly

Author: LawrenceOptify

jquery-ui-timepicker-addon.js

@@ -1768,7 +1768,7 @@
 		var off = date.getTimezoneOffset() * -1,
 			minutes = off % 60,
 			hours = (off - minutes) / 60;
-		return (off >= 0 ? '+' : '-') + ('0' + (hours * 101).toString()).substr(-2) + ('0' + (minutes * 101).toString()).substr(-2);
+		return (off >= 0 ? '+' : '-') + ('0' + (hours * 101).toString()).slice(-2) + ('0' + (minutes * 101).toString()).slice(-2);
 	};
 
 	/**
@@ -1880,4 +1880,4 @@
 	*/
 	$.timepicker.version = "1.1.2";
 
-})(jQuery);
+})(jQuery);