@eddy001 TOU tariffs need a calendar that maps peak, standard and off peak times.
The Calendar must map for the same time periods as what the Tariff has periods for.
On the Tools->Check Tariff Validity you should have a table of the Tariff Periods and each of the Calendar's periods linked to this Tariff.
You can change the Calendar's period for which it is valid under Tools->Certify TOU Calendar as valid.
Obviously you should only mark the Calendar valid for the periods that it is valid for.
So if it is subject to public holidays, make sure the public holidays for the whole date range is entered.