Creepy output of Date()-Function!

Using Swift
4

I’m not sure what your goal is, but setting a fixed-format date string without pinning the locale to en_US_POSIX is almost always a mistake. The three standard approaches for DateFormatter are:

  • If the date is meant to be seen (or input) by users, you should be using one of the predefined formats:

      let d = Date()
  let s1 = DateFormatter.localizedString(from: d, dateStyle: .short, timeStyle: .none)
  print(s1) // -> 04/03/2019

  • If you need more control over user-visible date strings, use a template:

      let df = DateFormatter()
  df.setLocalizedDateFormatFromTemplate("MM/yyyy")
  let s2 = df.string(from: d)
  print(s2) // -> 03/2019

  • If you’re dealing with date strings that aren’t user visible (from a network protocol header, for example), use either ISO8601DateFormatter or the en_US_POSIX locale.

Trying to mix’n’match these approaches generally doesn’t end well. QA1480 NSDateFormatter and Internet Dates has a specific example of how things can go wrong (but there are many others).

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Quinn “The Eskimo!” @ DTS @ Apple

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