I suppose, it needs to be done manually, at least until a proper #nostr feature is available: 1st figure out the time in hours and minutes the defined block was created, use

TIMECHAIN CALENDAR

Live data from the Bitcoin timechain with past block lookup and other calendar features.

2nd go through all the comments on your note where you announced the auction. The nostrich with the highest zap at the block time is the winner. Maybe @Leathermint has a plan to figure it out more efficiently? Tricky, if someone is zapping to late, but higher, could end up in a big disappointment?