NSDateComponents *_comps = [[NSDateComponents alloc] init];

[_comps setDay:19];

[_comps setMonth:4];

[_comps setYear:2016];

NSCalendar *gregorian = [[NSCalendar alloc]

initWithCalendarIdentifier:NSCalendarIdentifierGregorian];

NSDate *_date = [gregorian dateFromComponents:_comps];

NSDateComponents *weekdayComponents =

[gregorian components:NSCalendarUnitWeekday fromDate:_date];

NSInteger _weekday = [weekdayComponents weekday];

NSLog(@"_weekday:%ld",_weekday);

輸出結果為“1--7”的值，1代表星期日。