The first day on which a record or a setting is valid. The
effective date often includes the effective time.
In the actual set, or parameter set, the Effective Date field is empty, but the effective date is taken as the default value in the Description field.
In parameter sets that precede the actual set, the effective date is displayed in the Effective Date field.
If you make a change in the actual set, the changed set becomes the new actual set.