NSDatePicker setDate无法正常工作

Question

我正在尝试根据我以毫秒为单位的某个偏移量来设置NSDatePicker上的时间。设置时间后，看到的值不可用，我无法弄清楚原因。这是我用来设置选择器的代码：

- (void)setDatePicker{

    int targetmillisondsFromMidnight = [self.schedule.targetHour intValue]; //Value is: 61680000 milliseconds whis is equal to 17:08 UTC (or 19:08 in my local time);
    NSDate* todayMidnight = [NSCalendar.currentCalendar startOfDayForDate:[NSDate new]];
    NSTimeZone* timezone = [NSTimeZone localTimeZone]; //Value is: Local Time Zone (Asia/Jerusalem (GMT‎+2‎) offset 7200)
    NSInteger seconds = [timezone secondsFromGMT]; //Value is: 7200
    todayMidnight = [todayMidnight dateByAddingTimeInterval:seconds]; // Value is: 2019-12-25 00:00:00 UTC
    NSDate* scheduleDate = [NSDate dateWithTimeInterval:targetmillisondsFromMidnight/1000 sinceDate:todayMidnight]; //Value is: 2019-12-25 17:08:00 UTC

    NSCalendar *calendar = [NSCalendar currentCalendar];
    [calendar setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
    NSDateComponents *components = [calendar components:(NSCalendarUnitHour | NSCalendarUnitMinute) fromDate:scheduleDate];

    [self.datePicker setDate:[calendar dateFromComponents:components] animated:YES];
} 

我在函数的最后一个命令处以断点停下来，我打印了一些值，得到的输出是：po [components hour] = 17po [components minute] = 8po [calendar dateFromComponents:components] = 001-01-01 17:08:00 +0000

因此，根据我的理解，日期设置为17:08。我希望在时间选择器上看到的是19:08，但是我看到的是19:28。我不知道那20分钟是从哪里来的。

Answer 1

尝试此代码。日期选择器在设置时间当前时区时使用，并根据通过的日期（001-01-01 17:08:00 +0000）使用UTC偏移量，并在该时间点在时区数据库中查找偏移量。因为当时（零年没有时区，所以在tz数据库中找不到时区，所以根据平均太阳时间计算了时区偏移量，因此得到了偏移量2:20（大约。）在您所在的地区。

- (void)setDatePicker {
    int targetmillisondsFromMidnight = 61680000; //Value is: 61680000 milliseconds whis is equal to 17:08 UTC (or 19:08 in my local time);
    NSCalendar *calendar = NSCalendar.currentCalendar;
    NSTimeZone* timezone = [NSTimeZone timeZoneWithName:@"Asia/Jerusalem"]; //Value is: Local Time Zone (Asia/Jerusalem (GMT‎+2‎) offset 7200)
    calendar.timeZone = timezone;
    NSDate* todayMidnight = [calendar startOfDayForDate:[NSDate new]];

    NSInteger seconds = [timezone secondsFromGMT]; //Value is: 7200
    todayMidnight = [todayMidnight dateByAddingTimeInterval:seconds]; // Value is: 2019-12-25 00:00:00 UTC
    NSDate* scheduleDate = [NSDate dateWithTimeInterval:targetmillisondsFromMidnight/1000 sinceDate:todayMidnight]; //Value is: 2019-12-25 17:08:00 UTC

    NSDate *date = [scheduleDate dateByAddingTimeInterval:seconds];

    self.datePicker.timeZone = [NSTimeZone timeZoneWithAbbreviation:@"UTC"];
    [self.datePicker setDate:date animated:YES];
}