Question

I have the following code in an ASP.NET MVC3 Controller:

public PartialViewResult GetCalendar(int? month, int? year)
    {
        var test = new DateTime((year.HasValue ? year.Value : 1), (month.HasValue ? month.Value : 1), 1);
        return PartialView("Calendar", new DateTimeOffset(test));
    }

My view model is DateTimeOffset?

What is the reason for the exception thrown?

Answer 1

The DateTimeOffset constructor first converts any DateTime that is not of Kind ‘UTC’ to the equivalent UTC time. It will then check whether the UTC-equivalent DateTime falls outside of the bounds of DateTimeOffset.MinValue and DateTimeOffset.MaxValue, and if it does, will throw an ArgumentOutOfRangeException similar to the one you are experiencing.

Check the DateTime.Kind of the variable test that you are using, and if it is not ‘UTC’, work out if a conversion to UTC will make the DateTime specified by test fall outside of those bounds – according to the MSDN documentation, the MinValue and MaxValue (in UTC) are ‘1/1/0001 12:00:00 AM +00:00′ and ’12/31/9999 11:59:59 PM +00:00’ respectively.

The docs (DateTimeOffset.MinValue) note that:

“Any DateTimeOffset value is converted to Coordinated Universal Time (UTC) before the method performs the comparison with MinValue. This means that a DateTimeOffset value whose date and time are close to the minimum range, but whose offset is positive, may throw an exception. For example, the value 1/1/0001 1:00:00 AM +02:00 is out of range because it is one hour earlier than MinValue when it is converted to UTC.”

And also (DateTimeOffset.MaxValue):

“Any DateTimeOffset value is converted to Coordinated Universal Time (UTC) before the method compares it with MaxValue. This means that a DateTimeOffset value whose date and time are close to the maximum range, but whose offset is negative, may throw an exception. For example, the value 12/31/9999 11:00 PM -02:00 is out of range because it is one hour later than MaxValue when it is converted to UTC.”

And as per the docs (DateTimeOffset Constructor), the offset that is applied to a non-UTC Kind is the “offset of the local system’s current time zone”.