Switch Screen at Certain Time

I would like to switch to a default window at 12 am everyday no matter what window the client is currently in, what would my script need to look like?

Welcome to the forums.

This will open your window:

system.nav.openWindow('path/to/window')

I would personally use a Client Tag Change script for the trigger.
and the trigger tag would be an expression tag that goes high everyday at 12 am. (using dateExtract())

any idea what that would completely look like sorry im learning

Create your Trigger:
DateExtract: dateExtract - Ignition User Manual 8.0 - Ignition Documentation
your tag would be an expression tag (Boolean) with the following:

dateExtract(now(), 'hour') = 0 // boolean tag will be True everyday @ 12am.

Add trigger to Client Tag Event scripts (this link is for gateway Tag Events but the same applies for Clients):
https://docs.inductiveautomation.com/display/DOC80/Gateway+Event+Scripts#GatewayEventScripts-TagChangeScripts

Add the following script to the Client Tag Event Scripts Script tab:

system.nav.openWindow('path/to/window')