DST issue with Region and Time Zone

I am trying to retrieve dst end week and dst start week using .

//start week
unsigned char startWOMValue = (unsigned char)[calendar ordinalityOfUnit:NSCalendarUnitWeekOfMonth inUnit:NSCalendarUnitMonth forDate:dstStartDate];

//end week
unsigned char endWOMValue = (unsigned char)[calendar ordinalityOfUnit:NSCalendarUnitWeekOfMonth inUnit:NSCalendarUnitMonth forDate:dstEndDate];

I am able to get values. but when I tried to fetch dst end and start week after changing region from my ipad(language and region) and keeping time zone same. it was different.

Time Zone |Region |Dst start/end week values

Germany, Berlin |USA |05/05

Germany, Berlin |Germany |04/04

The upper one holds good but later one is not correct as per current DST in Germany. I want to achieve method by means of which I can remove dependency of DST from region.

Please suggest the way out.