Read-only OS time formatting preferences

[zbraniecki]

All operating systems allow user to select time format. Usually between 12h, 24h or follow automatic.

Firefox OS is currently providing navigator.mozHour12 that can take true/false/undefined values and that nicely fits into Intl API:

(new Date()).toLocaleString(navigator.languages, {
  hour12: navigator.mozHour12,
  hour: 'numeric',
  minute: 'numeric'
});

When "use default" is used, mozHour is undefined and Intl uses the default hour12 value for the given locale. If mozHour is specified to either true or false, Intl API follows that.

There's also an event associated with it: timeformatchange that is dipatched on window.

[zbraniecki]

There a several similar preferences that the API should either expose now, or be able to add in the future - timezone selection manual/automatic, showing/hiding dayperiod (am/pm) for 12h clock, showing/hiding seconds etc.

[annevk]

This is out-of-scope for DOM. I recommend filing this against https://github.com/whatwg/html.

[zbraniecki]

ugh, sorry! Filed in HTML: whatwg/html#171