某些日期的 DateFormatter.localizedString 已损坏 [英] DateFormatter.localizedString is broken for some of the dates

问题描述

这是我在选择器更改时所做的:

延期日期{var fromCurrentToUTC: 日期 {返回添加时间间隔(-TimeInterval(TimeZone.current.secondsFromGMT()))}}var title = "--"如果让日期 = datePickerView.date?.fromCurrentToUTC {title = DateFormatter.localizedString(from: date, dateStyle: .medium, timeStyle: .none)}打印(" -  - -")打印(datePickerView.date！)打印(标题)打印(时区.当前)打印(datePickerView.date！.timeIntervalSince1970)dateTimeSegmentControl.setTitle(title, forSegmentAt: 0)

这就是它查找日期的方式:

假设.11 月 6 日之前的日期一切正常，11 月 6 日之后一切都将关闭.为什么?

更新:

我使用的每个时区的关键日期都不同.例如:

华沙 (+0200) 日期是 10 月 30 日芝加哥 (-0500) 日期是 11 月 6 日

有序打印:

<前>-----2017-11-04 00:00:00 +00002017 年 11 月 4 日美国/纽约(当前)1509753600.0-----2017-11-05 00:00:00 +00002017 年 11 月 5 日美国/纽约(当前)1509840000.0-----2017-11-06 00:00:00 +00002017 年 11 月 5 日美国/纽约(当前)1509926400.0-----2017-11-07 00:00:00 +00002017 年 11 月 6 日美国/纽约(当前)1510012800.0

解决方案

在你的函数中

延期日期{var fromCurrentToUTC: 日期 {返回添加时间间隔(-TimeInterval(TimeZone.current.secondsFromGMT()))}}

减去当前日期的 GMT 偏移量，而不是由要调整的日期的 GMT 偏移量.因此你得到如果要调整的日期在 DST 期间而当前日期不在，则结果错误，反之亦然.

这可以通过使用来修复

延期日期{var fromCurrentToUTC: 日期 {return addedTimeInterval(-TimeInterval(TimeZone.current.secondsFromGMT(for: self)))}}

相反.但是，更好的解决方案是设置时区将日期格式化程序设置为 UTC，而不是调整日期:

if let date = datePickerView.date {让 fmt = DateFormatter()fmt.dateStyle = .mediumfmt.timeStyle = .nonefmt.timeZone = TimeZone(secondsFromGMT: 0)让 title = fmt.string(from: date)打印(标题)}

This is what I do when picker changes:

extension Date {
    var fromCurrentToUTC: Date {
        return addingTimeInterval(-TimeInterval(TimeZone.current.secondsFromGMT()))
    }
}    


var title = "--"

if let date = datePickerView.date?.fromCurrentToUTC {
    title = DateFormatter.localizedString(from: date, dateStyle: .medium, timeStyle: .none)
}

print("-----")
print(datePickerView.date!)
print(title)
print(TimeZone.current)
print(datePickerView.date!.timeIntervalSince1970)

dateTimeSegmentControl.setTitle(title, forSegmentAt: 0)

And this is how it looks for the dates:

Assuming. Everything is fine for the dates before 6th November, and everything is off after 6th November. Why?

update:

That critical date is different for every time zone I use. For example:

Warsaw (+0200) the date is 30 October Chicago (-0500) the date is 6th November

The ordered prints:

-----
2017-11-04 00:00:00 +0000
4 Nov 2017
America/New_York (current)
1509753600.0
-----
2017-11-05 00:00:00 +0000
5 Nov 2017
America/New_York (current)
1509840000.0
-----
2017-11-06 00:00:00 +0000
5 Nov 2017
America/New_York (current)
1509926400.0
-----
2017-11-07 00:00:00 +0000
6 Nov 2017
America/New_York (current)
1510012800.0

解决方案

In your function

extension Date {
    var fromCurrentToUTC: Date {
        return addingTimeInterval(-TimeInterval(TimeZone.current.secondsFromGMT()))
    }
} 

the GMT offset of the current date is subtracted, not by the GMT offset of the date to be adjusted. Therefore you get a wrong result if the date to be adjusted is in a DST period and the current date is not, or vice versa.

That can be fixed by using

extension Date {
    var fromCurrentToUTC: Date {
        return addingTimeInterval(-TimeInterval(TimeZone.current.secondsFromGMT(for: self)))
    }
} 

instead. However, a better solution would be to set the timezone of the date formatter to UTC, instead of adjusting the date:

if let date = datePickerView.date {
    let fmt = DateFormatter()
    fmt.dateStyle = .medium
    fmt.timeStyle = .none
    fmt.timeZone = TimeZone(secondsFromGMT: 0)
    let title = fmt.string(from: date)
    print(title)
}

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