确定给定年份的阵亡将士纪念日的NSDate

Question

是否有更好的方法来确定特定年份阵亡将士纪念日（5月的最后一个星期一）的NSDate？

NSInteger aGivenYear = 2013 ;

NSCalendar* calendar = [NSCalendar currentCalendar] ;
NSDateComponents* firstMondayInJuneComponents = [NSDateComponents new] ;
firstMondayInJuneComponents.month = 6 ;
// Thanks, Martin R., for pointing out that `weekOfMonth` is wrong for returning the first Monday in June.
firstMondayInJuneComponents.weekOfMonth = 1 ;
firstMondayInJuneComponents.weekday = 2 ; //Monday
firstMondayInJuneComponents.year = aGivenYear ;
NSDate* firstMondayInJune = [calendar dateFromComponents:firstMondayInJuneComponents] ;

NSDateComponents* subtractAWeekComponents = [NSDateComponents new] ;
subtractAWeekComponents.week = 0 ;
NSDate* memorialDay = [calendar dateByAddingComponents:subtractAWeekComponents toDate:firstMondayInJune options:0] ;

修改的

我现在看到上面例子中的firstMondayInJune并不适用于所有年份;它返回2012年5月28日。

谢谢，Martin R。 weekdayOrdinal完全按照我的意愿行事，它会在纪念日返回3行代码：

NSInteger aGivenYear = 2013 ;

NSDateComponents* memorialDayComponents = [NSDateComponents new] ;
memorialDayComponents.year = aGivenYear ;
memorialDayComponents.month = 5 ;
memorialDayComponents.weekday = 2 ; //Monday
memorialDayComponents.weekdayOrdinal = -1 ; //The last instance of the specified weekday in the specified month & year.
NSDate* memorialDay = [calendar dateFromComponents:memorialDayComponents] ;