Comparing Date objects; 1 hour difference

Using a plugin i have 2 custom pickerfields where you can select a date(but without the year) and time. This way you can say that for example on 22 of april, i've started working on 09:05 and ended at 17:35. When these fields are initiated the get a value of new Date(), so it will be set to the current time and date.

I want to calculate the worked time, but for some reason the calculated time is always off by +1 hour.

The code from a pickerfield:

Code:

{    xtype: 'datetimefield',
    itemId: 'startTimeField',
    label: 'Start tijd',
    value: new Date(),
    dateTimeFormat : 'd-m-Y H:i',
    picker: {
        useTitles: true,
        yearFrom: 1980,
        ampm : false,
        slotOrder: ['day', 'month', 'hour', 'minute'],
        listeners: {
            change: function(me, value){
                var endTimeField = this.getParent().down('#endTimeField');
                var timeEnd = endTimeField.getValue();
                var timeStart = value;
                
                console.log('start: '+timeStart.getTime()+' end: '+timeEnd.getTime());
                
                var diff = Math.abs(timeStart.getTime() - timeEnd.getTime())
                var time = Ext.Date.format(new Date(diff), 'H:i');
                console.log(time);
                
                var elapsed = Ext.Date.getElapsed(timeStart, timeEnd);
                var time2 = Ext.Date.format(new Date(elapsed), 'H:i');
                console.log(time2);
            }
        }
    }
},

timeEnd and timeStart are both Date objects and in the first console.log i notice there is a small difference between them: start: 1398147960000 end: 1398151585216. When i calculate the difference between them and create new Date objects from this calculated result the elapsed time is always the correct time but +1 hour.

So when i set the first picker field to 09:05 and the second to 10:10 the calculated difference will be 02:05. The minutes always seem correct but the hours are always off. As you can see i tried using the Sencha method Elapsed but also the math version of it, but both with the same result.

Is this a bug or something?