Get first day of the current week as NSDate

gistfile1.txt

- (void)test_printDateVariants {
    NSDateFormatter *fmt = [NSDateFormatter new];
    NSTimeZone *timezone = [NSTimeZone timeZoneWithName:@"UTC"];
    [fmt setTimeZone:timezone];
    [fmt setDateFormat:@"yyyy-MM-dd hh:mm:ss Z"];
    
    
    NSCalendar *calendar = [NSCalendar currentCalendar];
    
    for(int i = 1;i <= 31; ++i) {
        [fmt setDateFormat:@"yyyy-MM-dd hh:mm:ss Z"];
        NSDate *date = [fmt dateFromString:[NSString stringWithFormat:@"2016-05-%02d 10:08:24 +0800", i]];
        NSInteger firstdayOfWeek = [calendar ordinalityOfUnit:NSWeekdayCalendarUnit inUnit:NSWeekCalendarUnit forDate:date] - 1;
        NSDate *newDate = [NSDate dateWithTimeInterval:(-firstdayOfWeek * (60 * 60 * 24)) sinceDate:date];
        [fmt setDateFormat:@"dd"];
        NSLog(@"date: %@, firstdayOfWeek: %lu", [fmt stringFromDate:newDate], firstdayOfWeek);
    }
}