同一日期的 NSDate 和 NSDateComponent 值之间的差异

Question

我创建了一个简单的函数来获取一周中一天的第一天和最后一天。 查看 NSLog 输出，我发现同一日期的 NSDate 描述符和组件日返回不同的值，为什么？

这里 NSLog 输出：

NSDATE: 2011-04-03 22:00:00 +0000, DAY COMPONENT: 4 
NSDATE: 2011-04-09 22:00:00 +0000, DAY COMPONENT: 10 

如您所见，第一行的 NSDATE 是 4 月 3 日，日期部分是 4，第二行分别是 9 和 10。

这里是代码：

NSDate *date = [NSDate date]; //Today is  April 5th 2011
NSCalendar *cal =[[NSCalendar alloc]initWithCalendarIdentifier:NSGregorianCalendar];

[cal setFirstWeekday:2]; //My week starts from Monday

//DEFINE BEGINNING OF THE WEEK
NSDate *beginningOfWeek = nil;
[cal rangeOfUnit:NSWeekCalendarUnit startDate:&beginningOfWeek interval:nil forDate:date];
NSDateComponents *beginComponents = [cal components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSWeekCalendarUnit | NSWeekdayCalendarUnit) fromDate:beginningOfWeek];

//DEFINE END OF THE WEEK, WITH 6 days OFFSET FROM BEGINNING
NSDateComponents *offset = [[NSDateComponents alloc]init];
[offset setDay:6];
NSDate *endOfWeek = [cal dateByAddingComponents:offset toDate:beginningOfWeek options:0];
NSDateComponents *endComponents = [cal components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSWeekCalendarUnit | NSWeekdayCalendarUnit) fromDate:endOfWeek];

NSLog(@"NSDATE: %@, DAY COMPONENT: %d",beginningOfWeek, [beginComponents day]);
NSLog(@"NSDATE: %@, DAY COMPONENT: %d",endOfWeek,       [endComponents day]);

Answer 1

您的日期打印时区为 +0000 (UTC)，而您的 NSCalendar 实例（以及您的 NSDateComponents）正在使用设备的默认时区（我猜是 UTC+2）。