You can get a list of supported locales from [`locale.list_avail()`](https://github.com/saltstack/salt/blob/develop/salt/modules/localemod.py#L70), however, you  have to know each for locales date format to be able to parse it.

Passing `C` as `LC_TIME` does not restrict you to any locale formatting though, the date format presented is not the best:

```
$ LC_TIME=C who
vampas   tty7         Dec  3 09:35 (:0)
vampas   pts/2        Dec  3 09:35 (:0)
vampas   pts/0        Dec  3 10:02 (:0)
vampas   pts/7        Dec  3 10:10 (:0)

$ LC_TIME=pt_PT.UTF-8 who
vampas   tty7         2013-12-03 09:35 (:0)
vampas   pts/2        2013-12-03 09:35 (:0)
vampas   pts/0        2013-12-03 10:02 (:0)
vampas   pts/7        2013-12-03 10:10 (:0)
```