How to compare 12-hour/24-hour formatted time strings in C#?

Question

How do I compare which time string is greater; be it in 24-hour or 12-hour format?

For example, "9:42:54" vs "19:25:31" or "9:42:54 AM" vs "7:25:31 PM".

Answer 1

To be able to compare strings in time format, you need to convert them to TimeSpan or DateTime objects, but the former seems to be more relevant:

TimeSpan time1 = TimeSpan.Parse("9:42:54");
TimeSpan time2 = TimeSpan.Parse("19:25:31");

or

TimeSpan time1 = DateTime.Parse("9:42:54").TimeOfDay;
TimeSpan time2 = DateTime.Parse("19:25:31").TimeOfDay;

However, using TimeSpan.Parse for 12-hour time string formats will throw a System.FormatException. Use DateTime.Parse instead and take only the time part of the created DateTime object:

TimeSpan time1 = DateTime.Parse("9:42:54 AM").TimeOfDay;
TimeSpan time2 = DateTime.Parse("7:42:54 PM").TimeOfDay;

As a benefit, converting to TimeSpan will also give you a chance to apply TimeSpan operators like regular comparison, subtraction, addition, etc.:

if (time1 > time2)
{
    // time1 is greater
}
else if (time1 < time2)
{
    // time2 is greater
}
else
{
    // They are equal
}

You can also use TimeSpan.ParseExact if you need to the specify the time format of your string explicitly.