The A check has to be perfomed every week. So, unlike the B check, you have to allow time in the aircraft schedule for the A check, which is 5 hours.
2 Solutions, one is to shift the schedule about, move the A check to 0200 and cut 10 minutes from turnaround times somewhere. The other is to set the last flight not to run on the day of the check.
P.S. If you are going to go with the second option, might be best to move the check to saturday, as that's when demand is generally at it's lowest.