DateFormatter.localizedString is broken for some of the dates - ios

Question

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

Answer 1

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)
}