Tim Streater put finger to keyboard:
True, although 24:00 is used to denote exactly the start of 00:00 the following day.
For example in car insurance, if your old policy runs out on 30/01/15 at
23:59 and the new one starts on 31/01/15 at 0:00 then what's the score on the 30th at 23:59 and 30 seconds? Saying the old policy expires on 30/01/15 at 24:00 is intended to clarify that the extra minute between 23:59 and 00:00 is indeed covered. I would argue that there are better and clearer ways of communicating that fact, but there you have it.