Clear times, fair exceptions and a record of both.
01Always say the timezone
'Friday 23:59' means different things to different people. Show the timezone everywhere the deadline appears.
02Give a receipt
A receipt code and timestamp settles most 'did it go through?' questions before they reach your inbox.
03Treat exceptions as exceptions
Extend one team's deadline instead of everyone's, and record why. Reopen a round only with a visible reason, and mark anything after the deadline as late.