Returns date of yesterday.

yesterday

-(NSDate *)yesterday {
    NSCalendar *cal = [NSCalendar currentCalendar];
    NSDate *now = [NSDate date];
    NSDateComponents *comp = [cal components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit fromDate:now];
    comp.timeZone=[NSTimeZone defaultTimeZone];
    comp.month = comp.month;
    comp.year = comp.year;
    comp.day = comp.day-1;
    [comp setHour:0];
    [comp setMinute:0];
    [comp setSecond:0];
    NSDate *yesterday = [cal dateFromComponents:comp];
    return yesterday;
}