This refers to the actual date that the event will end. Hosting a multi-day festival? What is the date of the final day?
This number is purely meant to outline the timeframe in which the event takes place. It will have no bearing on when POAPs can be reserved or minted.
This refers to the date that the POAP will no longer be reservable or mintable. Beyond this date, collectors who have been given a mint link, Secret, Delivery page, etc., will not be able to use these to mint a new POAP.
Users who reserve the POAP with an email address prior to this date will still (and forever) be able to mint the POAP to an Ethereum address.