better variable name

lib/timeline/DateUtil.js

@@ -299,9 +299,9 @@ exports.toScreen = function (Core, time, width) {
       var duration = exports.getHiddenDurationBetween(Core.body.hiddenDates, Core.range.start, Core.range.end);
       if (time < Core.range.start) {
         var conversion = Core.range.conversion(width, duration);
-        var durationAfter = exports.getHiddenDurationBeforeStart(Core.body.hiddenDates, time, conversion.offset);
+        var hiddenBeforeStart = exports.getHiddenDurationBeforeStart(Core.body.hiddenDates, time, conversion.offset);
         time = Core.options.moment(time).toDate().valueOf();
-        time = time + durationAfter;
+        time = time + hiddenBeforeStart;
         return -(conversion.offset - time.valueOf()) * conversion.scale;
         
       } else if (time > Core.range.end) {