DateTime fails to parse 24:00:00 in the HH:mm:ss format

Question

I noticed quite an interesting error when parsing some times.

DateTime fails to parse 24:00:00. Under some Googling and Stacking, I found out that DateTime only recognizes 00 - 23 (what the?????), so if your input is 24:00:00, you're out of luck. You would think someone would put in a condition to equate 24:00:00 as 00:00:00 (the midnight), but not yet..

My question is, how do I allow DateTime to allow me to parse 24:00:00?

Unfortunately I cannot to use NodaTime under specification reasons (sorry Jon. I love your library though).

Experimentation below:

An input of 2014-03-18 24:00:00 would present the following error. Expected.

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An input of 2014-03-18 23:59:59 would successfully parse. Expected.

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An input of 2014-03-19 00:00:00` would successfully parse. Expected.

Answer 1

There is no "24th hour" support in the DateTime class.

The hour (HH/H, 24-hour clock) must be 0-23, inclusive. This is why 00:00:00 is valid, but 24:00:00 is not.

Change 24:00:00 to 00:00:00 (before parsing) and, if needed, advance the day as appropriate (after parsing).

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The following will work on times in the provided format (but only up to the 24th hour) although it doesn't account for an arbitrary format. Supporting different format strings only adds additional complications.

DateTime ParseWithTwentyFourthHourToNextDay (string input) {
    var wrapped = Regex.Replace(input, @"24:(\d\d:\d\d)$", "00:$1");
    var res = DateTime.ParseExact(wrapped, "yyyy-MM-dd HH:mm:ss", null);
    return wrapped != input
        ? res.AddDays(1)
        : res;
}

Answer 2

24:00:00 doesn't exist. It is 00:00:00 - 23:59:59