TimeTrex Time and Attendance

i saw it and this what i didn't understand the difference between "have no effect" and "Never on Holidays" in date type holidays
for me it mean's the same.
could you explain me by example the meaning Never on holidays and have no effect.
thank you.

Hello;

i m trying to set up my premium policy but i was wondering in holiday pick list what is the difference between "have no effect" and "Never on Holidays"

i appreciate your help.

thank you