How to get first day of the week in IOS

Question

Possible Duplicate:
NSCalendar first day of week

I need first date of the week for that I'm having weekNumberOfThe Year and Year.

I got this solution:

[components setYearForWeekOfYear:year];
[components setWeekOfYear:week];
[components setWeekday:2];

This is working on IOS 5 +, but not working on IOS less than 5, i.e. 4 and 4.3 likewise