[IoNut1290]

You don't use amx_ commands ! This is the server doing the changes not the admin.

For your problem you have to write

"00:00" "say Example"
"00:00" "mp_timelimit 0"

If you are afraid about the cvar set when you want to exit the night program "08:00" "mp_timelimit 30" (I've put 8 and 00 as a example)