Nsryjdtyk

When generating date formats from a template with Foundation's DateFormatter for the Locale "de", like this:

let locale: Locale = Locale(identifier: "de")

let format = DateFormatter.dateFormat(fromTemplate: "dMMMyGhhmmss",

                                      options: 0,

                                      locale: locale)

I always get this format:

d. MMM y G, h:mm:ss a

which renders

17. Nov. 2018 n. Chr., 8:30:20 PM

The 'PM' part is unusual for Locale "de", but it is my understanding that this method also takes user preferences into account. Is that correct?

I played around with the settings in System Preferences, e.g. switching to 24-hour clock, but nothing I changed had any effect. Do I have to restart something for the changes to take effect?

Can someone explain to me what's going on?

If you use h or H in the template, the format will contain the specified hour format (12-hour or 24-hour), regardless of the locale. Use j instead. This symbol requests the preferred hour format for the locale.

For example, given the template dMMMyGjjmmss, I get:

• 
  MMM d, y G, h:mm:ss a (12-hour format) for locale "en"


• 
  d. MMM y G, HH:mm:ss (24-hour format) for locale "de"

Apple's documentation states:

The format string uses the format patterns from the Unicode Technical Standard #35.

The Unicode Technical Standard #35 has this to say about the symbol j:

This is a special-purpose symbol. It must not occur in pattern or skeleton data. Instead, it is reserved for use in skeletons passed to APIs doing flexible date pattern generation. In such a context, it requests the preferred hour format for the locale (h, H, K, or k), as determined by whether h, H, K, or k is used in the standard short time format for the locale. In the implementation of such an API, 'j' must be replaced by h, H, K, or k before beginning a match against availableFormats data. Note that use of 'j' in a skeleton passed to an API is the only way to have a skeleton request a locale's preferred time cycle type (12-hour or 24-hour).