How can I shutdown a RHEL server at 06:45 tomorrow morning?

I just received notification that our site has a power outage tomorrow morning.

I am a Windows admin but I have to cover for our Linux admin who's not around until tomorrow evening.

I need to shutdown our RHEL server at 06:45 tomorrow morning (without me doing it).

I have searched on here but see mixed answers using shutdown, some say -h, some say -p, some say something completely different.

It's ~21:15 now and I need to shutdown at 06:45 in the morning. What is the simplest way I can schedule this?