Comment 6 for bug 1375890

To be fair, although the locale-provided format is a good default, it's still not ideal. The user should be able to specify their own formats. For example, the US "MM/DD/YY h:mm pm" format is pretty terrible, and I can't force it to something sane like 24-hour time with an ISO-standard date "YYYY-MM-DD HH:mm".