Is it possible to schedule the number of instances in a fleet?

Have you tried the GameLift scale settings to allow the lowest instance to be zero?

The way I've solved this in the past is to have a scheduled lambda, runs at fixed time to scale all fleets to zero if any are scaled up

First developer in then scales the fleets required up (you could also have another scheduled lambda to scale up fleets required).

Yes, I did but I manually did it. So now I'm looking for something like a scheduler.

Thanks Pip. I'll look into it.