system times for SEPM and SEP clients are in sync. MON_RARALIO...I don't follow--from how I read your comment, you are saying it's possible for clients to continue to upgrade after the specified time because of when they checked in with the SEPM.
But that isn't what I'm seeing--clients are upgrading before the time specified, as if the set schedule didn't exist and they started upgrading as soon as they checked in with the SEPM and saw that an upgrade package was available.