As with Kusama, each seven-day auction on Polkadot will consist of a starting period of one day and 21 hours, followed by an ending period of five days. Bidding ends on the seventh day, when the precise moment of the auction’s close is determined retroactively by an on-chain, verifiable random function (VRF).
Polkadot Sets Date for Hotly Anticipated Parachain Auctions — CoinDesk
