Question

I have NSDate* day1 and NSDate* day2. How can I make a NSDate* day3 by copying only year/month/day from day1 and hour/minute/second from day2?

Answer 1

unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
NSDateComponents *comps = [[NSCalendar currentCalendar] components:unitFlags fromDate:day1];
NSDate *day3 = [[NSCalendar currentCalendar] dateFromComponents:comps];

unitFlags = NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
comps = [[NSCalendar currentCalendar] components:unitFlags fromDate:day2];
day3 = [[NSCalendar currentCalendar] dateByAddingComponents:comps toDate:day3 options:0];

Sources:

1. NSDateComponents Class Reference
2. NSCalendar Class Reference