Is your feature request related to a problem? Please describe.
DateTime::from_msdos can create a DateTime value even if datepart or timepart is an invalid value.

Describe the solution you'd like
I would like one of the following:

A clear and concise description of what you want to happen.

1. Make DateTime::from_msdos an unsafe function.
2. Returns Err if datepart or timepart is invalid.
3. Panics if datepart or timepart is invalid.

Describe alternatives you've considered
Specify in the documentation that an invalid DateTime value may be created.