C# TimeSpan.Parse invalid format returns incorrect value instead of exception

Question

TimeSpan.Parse("23:00:00") returns 23 hours.

TimeSpan.Parse("24:00:00") returns 24 days!

I realize that I made a mistake in that the allowable range of hours is 0-23. But for minutes and seconds if you attempt to parse an out of range value you get an exception. In the case of hours with an out of range value, the parser incorrectly assumes you meant days instead of hours.

Can someone explain this?

This example here covers this very topic and indicates that http://msdn.microsoft.com/en-us/magazine/ee309881.aspx

The same appears to be true about TryParse. I get 24 days despite the docs stating that the parse should fail.

http://msdn.microsoft.com/en-us/library/3z48198e

//            String to Parse                TimeSpan
//            ---------------   ---------------------
//                          0        00:00:00
//                         14     14.00:00:00
//                      1:2:3        01:02:03
//                  0:0:0.250        00:00:00.2500000
//             10.20:30:40.50     10.20:30:40.5000000
//        99.23:59:59.9999999     99.23:59:59.9999999
//        0023:0059:0059.0099        23:59:59.0099000
//                     23:0:0        23:00:00
//                     24:0:0   Parse operation failed.
//                     0:59:0        00:59:00
//                     0:60:0   Parse operation failed.
//                     0:0:59        00:00:59
//                     0:0:60   Parse operation failed.
//                        10:   Parse operation failed.
//                       10:0        10:00:00
//                        :10   Parse operation failed.
//                       0:10        00:10:00
//                     10:20:   Parse operation failed.
//                    10:20:0        10:20:00
//                       .123   Parse operation failed.
//                    0.12:00        12:00:00
//                        10.   Parse operation failed.
//                      10.12   Parse operation failed.
//                   10.12:00     10.12:00:00

Did I find a bug or am I doing something wrong?

EDIT: I've tested this in LinqPad and using a Console app in .NET4 on Windows 7 64bit.

            var result = TimeSpan.Parse("24:00:00");
            Console.WriteLine(result);
            result = TimeSpan.Parse("24:00:00", CultureInfo.InvariantCulture);
            Console.WriteLine(result);

This results in:

24.00:00:00
24.00:00:00

Answer 1

What's going on is that TimeSpan.Parse attempts to parse ##:##:## using each of the following formats in order, stopping as soon as one succeeds:

1. hh:mm:ss (invariant culture)
2. d.hh:mm (invariant culture)
3. hh:mm:ss (localized)
4. d.hh:mm (localized; more details about the "." below)

So:

• 23:08:09 is successfully parsed as 0d 23h 8m 9s in Step 1.
• 24:08:09 is successfully parsed as 24d 8h 9m 0s in Step 4.

If this behavior doesn't suit you, you can use TimeSpan.ParseExact instead:

TimeSpan.ParseExact("23:00:00", "hh':'mm':'ss", null) // OK
TimeSpan.ParseExact("24:00:00", "hh':'mm':'ss", null) // OverflowException

UPDATE: According to the documentation for TimeSpan.Parse, the "." between "d" and "hh" is

A culture-sensitive symbol that separates days from hours. The invariant format uses a period (".") character.

However, I dug into the framework source with Reflector, and it turns out that, in the localized format, this alleged "culture-sensitive" symbol is always a colon! Here's an excerpt from the internal DateTimeFormatInfo.FullTimeSpanPositivePattern property:

string separator = new NumberFormatInfo(cultureData).NumberDecimalSeparator;
this.m_fullTimeSpanPositivePattern = "d':'h':'mm':'ss'" + separator + "'FFFFFFF";