Hey Garron,
You use the IsDateValid() function to check dates of feature values of Date/Time type. For instance, create a feature value "update_expires", and have the value set to a year from now. From now until 1 year from now IsDateValid() will return true when you pass in the feature value for "update_expires" (using GetFeatureValue() ).
If you want to use your own date checking then you certainly can. IsDateValid() is a convenience function.
Does that make sense?