The days that APD rules do not apply are in the contract but you can still use an APD on the days listed as being restricted. The only difference is that the normal APD reduction in reserves required to drop do not apply. The advantage is that APDs run before PDs so if the day in question is still net positive but very tight, you may still be able to drop Christmas, Thanksgiving, etc. Obviously this would probably only work for the first PCS run of a bid period.