While the exact number of blocks varies depending on the blockchain protocol, an “epoch” generally refers to a specific or approximate period of time. Different PoS protocols have different ways of defining an epoch, which is commonly found on blockchains that use Proof of Stake (PoS) (if they do). To reach security checkpoints, distribute staking rewards, or assign a new group of blockchain validators, epochs are used. An Ethereum epoch, for example, lasts 30,000 blocks, whereas a Cardano epoch lasts five days.