Regular expression for matching HH:MM time format

Question

I want a regexp for matching time in HH:MM format. Here\'s what I have, and it works:

^[0-2][0-3]:[0-5][0-9]$

This matches everything from

Answer 1

Amazingly I found actually all of these don't quite cover it, as they don't work for shorter format midnight of 0:0 and a few don't work for 00:00 either, I used and tested the following:

^([0-9]|0[0-9]|1?[0-9]|2[0-3]):[0-5]?[0-9]$