One way to do that is to parse new Date().toLocaleString().
But this doesn\'t work in chromium/webkit since the string it returns isn\'t dependent of the user\'
I know it would be the least favoured way of doing it, but could you not just check the time?
If the time is before 12, set the time to 1pm and test if the output is 13 or 1.
I know its a shoehorn of an idea, but if placed into a nice Date.prototype.is24hour(), returns true; It could work nicely?
I use http://www.datejs.com/ with dates. tends to do everything I need! So you could use that alongside a custom prototype function, and that would give you what you need!