24-hour vs 12-hour... option?

Am I missing where this option might exist? All my images are being renamed based on a 12-hour clock, but I would prefer to use what we call here in the states, "military time" which is the 24-hour clock. Is there a way to change the 12-hour default to be the 24-hour format? I feel this would my file names cleaner and easier to sort. Thanks.

Insufficient information

Reply to #2:

When using a tag like <Hour>, it will output "11" for both 11:00 AM and 11:00 PM. It would be nice to have an option (like <Hour:24>) to output the hour in the 24h format : "11" for 11:00 AM and "23" for 11:00 PM. Every "Hour" tags should have this option.

Reply to #3:
It's trivial to accomplish this with some simple JavaScript:

eg

hour = app.parseTags("<Hour>");
hour = (hour>12) ? (hour-12)+"pm" : hour+"am";