I haven’t used any commands to get the OS time but you can always make an in-game clock(quite easy to make can take 5 minutes or less) I can help with that if needed.
And I guess every 30 minutes you can do a check on all AI to see if they have a job scheduled.
So for example at 6:00 do “get all actors of class” - “Postman”.
This will get all the actors of type postman.
You can then run function in them - this function could be what makes them go out to work - or it might just be a variable that is picked up from the AI behaviour tree blackboard.