NSDateComponents组件：fromDate和Time Zones

3 回答

• 5

  问题是，GMT不等于英国夏令时 . 日期 2010-08-02 08:00:00 +0100 等于 2010-08-02 07:00:00 GMT 所以7小时是你应该得到的结果 .

  回复于 2024-04-29T15:15:30+08:00
• 15

  另请注意， NSDate 对象始终根据GMT显示时间，而您从该日期拉出的组件会被 timeZoneWithName 部分更改 .

  例：

  NSDate *today = [NSDate date];
  NSLog(@"Today's date: %@",today);
  
  unsigned hourAndMinuteFlags = NSHourCalendarUnit | NSMinuteCalendarUnit;
  NSCalendar* calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
  [calendar setTimeZone:[NSTimeZone timeZoneWithName:@"GMT"]];
  NSDateComponents* travelDateTimeComponents = [calendar components:hourAndMinuteFlags fromDate:today];
  NSString* hours = [NSString stringWithFormat:@"%02i", [travelDateTimeComponents hour]];
  NSString* minutes = [NSString stringWithFormat:@"%02i", [travelDateTimeComponents minute]];
  
  NSLog(@"Calendar: %@",calendar);
  NSLog(@"Travel Components: %@",travelDateTimeComponents);
  NSLog(@"Hours: %@",hours);
  NSLog(@"Minutes: %@",minutes);
  

  控制台输出：

  [Session started at 2011-01-23 12:59:17 -0700.]
  2011-01-23 12:59:19.755 testttt[5697:207] Today's date: 2011-01-23 19:59:19 +0000
  2011-01-23 12:59:19.756 testttt[5697:207] Calendar: <__NSCFCalendar: 0x4b2ca70>
  2011-01-23 12:59:19.757 testttt[5697:207] Travel Components: <NSDateComponents: 0x4b2de20>
  2011-01-23 12:59:19.757 testttt[5697:207] Hours: 19
  2011-01-23 12:59:19.758 testttt[5697:207] Minutes: 59
  

  现在，如果我们改变时区......

  NSDate *today = [NSDate date];
  NSLog(@"Today's date: %@",today);
  
  unsigned hourAndMinuteFlags = NSHourCalendarUnit | NSMinuteCalendarUnit;
  NSCalendar* calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
  [calendar setTimeZone:[NSTimeZone timeZoneWithName:@"MST"]];
  NSDateComponents* travelDateTimeComponents = [calendar components:hourAndMinuteFlags fromDate:today];
  NSString* hours = [NSString stringWithFormat:@"%02i", [travelDateTimeComponents hour]];
  NSString* minutes = [NSString stringWithFormat:@"%02i", [travelDateTimeComponents minute]];
  
  NSLog(@"Calendar: %@",calendar);
  NSLog(@"Travel Components: %@",travelDateTimeComponents);
  NSLog(@"Hours: %@",hours);
  NSLog(@"Minutes: %@",minutes);
  

  输出：

  2011-01-23 13:05:29.896 testttt[5723:207] Today's date: 2011-01-23 20:05:29 +0000
  2011-01-23 13:05:29.897 testttt[5723:207] Calendar: <__NSCFCalendar: 0x4e10020>
  2011-01-23 13:05:29.897 testttt[5723:207] Travel Components: <NSDateComponents: 0x4e0f6d0>
  2011-01-23 13:05:29.898 testttt[5723:207] Hours: 13
  2011-01-23 13:05:29.898 testttt[5723:207] Minutes: 05
  

  请注意当地时间和分钟如何变化，但“今天的日期：”部分仍然反映了GMT . 如果你问我，有点误导程序员 .

  回复于 2024-04-29T15:15:30+08:00
• 3

  我同意aqua . 这是非常误导，并让我几天撞到屏幕上 . 它的工作方式如下：[NSDate date]始终返回当前日期 . 所以在上面的例子中它将是2010-08-02 08:00:00 . 当我们转换为NSDateComponents时，实际时间会丢失并转换为一组不再占用时区的整数（小时，年等） .

  当转换回NSDate对象时，它将采用年，月，日等的值并相对于GMT给你，因此丢失了一小时 . 这就是它在框架中决定的方式 . 我所做的是以下内容：

  +(NSDateComponents *)getComponentFromDate:(NSDate *)date {
  
      NSCalendar * gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
  
      unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSWeekdayCalendarUnit | NSDayCalendarUnit;
      NSDateComponents* components = [gregorian components:unitFlags fromDate:date];
  
      NSTimeZone* timeZone = [NSTimeZone localTimeZone];
      if(timeZone.isDaylightSavingTime) components.hour = ((int)timeZone.daylightSavingTimeOffset/3600);
  
      [gregorian release];
  
      return components;
  }
  

  这将给我一个舍入到当天的组件的“更正”版本，当传递到日历以检索日期时，将始终设置为作为参数传递的日期的00:00:00 .

  回复于 2024-04-29T15:15:30+08:00