Set an empty DateTime variable

Since DateTime is a value type you cannot assign null to it, but exactly for these cases (absence of a value) Nullable<T> was introduced - use a nullable DateTime instead:

DateTime? myTime = null;

No. You have 2 options:

DateTime date = DateTime.MinValue;

This works when you need to do something every X amount of time (since you will always be over MinValue) but can actually cause subtle errors (such as using some operators w/o first checking if you are not MinValue) if you are not careful.

And you can use Nullable:

DateTime? date = null;

Which is nice and avoids most issues while introducing only 1 or 2.

It really depends on what you are trying to achieve.

You can set a DateTime variable to be '1/1/0001 00:00:00' but the variable itself cannot be null. To get this MinTime use:

DateTime variableName = DateTime.MinValue;