"Also, 2400 is perfectly valid and often used in place of 0000."
Hmm, not too keen on that. According to the gospel (well, Ellis' British Railway Engineering Encyclopaedia):
Midnight: since 00:00 is ambiguous (is it later today, early tomorrow, or was it first thing?) railway practice avoids it and uses 23:59 or 00:001 instead, as required. For all practical puposes the intervening two minutes do not exist.