Why does this attempt to parse DateTime fail?

Question

This:

bool ret = DateTime.TryParse("Sunday 11 November", out date);

fails to parse the date string? Why?

I realize the string is an incomplete date, but why can't the framework handle it? Does the framework always try to return a legitimate date? Because if so, that would explain it (Sunday 11th November 2014 is not a valid date)

Answer 1

It's easy enough to verify, just change the date to a valid one (Sunday 9 November), and guess what, it works. You will also see that the year is set to 2014.

So yes, it appears that if the date is not valid, parsing will fail.

Answer 2

In the documentation for DateTime.TryParse, it states the following:

This method tries to ignore unrecognized data, if possible, and fills in missing month, day, and year information with the current date.

In your example, the year is missing, so it will plug in the current year, giving Sunday 11 November 2014. I'm assuming it is invalid because the 11th of Nov does not fall on a Sunday. The documentation does include examples that include the name of the day.

It's funny to see this question, because this non-intuitive feature of TryParse (filling in missing parts) bit someone in my office just today.