Calling ToString("YYYY-mm-dd") results in wrong date format

Question

I've got a constructor which takes a DateTime object:

public Report(DateTime date, string start = "0", string end = "0")
{
    Logger.Info("Creating a new Report...");

    StartTime = start;
    EndTime = end;
    Date = date.ToString("YYYY-mm-dd");

    SetStartEndTimes();

    Logger.Info("Report Created");
}

Now, this was working fine just 3 days ago. However, I come back today, after a break, and this is the results I'm seeing:

As you can see, the date being passed in is right. However, after the format, it is not. Again, this worked before my break. I come back, and I get this. Am I missing something? Why would it format so incorrectly after working since the beginning?

EDIT

Thanks guys. The messed up part is looking through the source control at previous versions, this worked. Or maybe I imagined it working. I don't know. But it's been this way for about 3 months.

Answer 1

Year must be lowercase and month uppercase:

Date = date.ToString("yyyy-MM-dd");  // btw, lowercase mm means minutes

Custom Date and Time Format Strings