Epoch

An epoch is a fixed span of time or blocks that a blockchain uses as an organizational unit for scheduling consensus duties, distributing rewards, or applying parameter changes. Rather than making every decision block by block, many protocols batch bookkeeping into these regular intervals: validator assignments are drawn up for the coming epoch, and results are tallied when it ends.

Ethereum defines an epoch as 32 slots of 12 seconds each — about 6.4 minutes. At each epoch boundary the protocol shuffles which validators attest in which slots, processes entries and exits from the validator set, and evaluates finality: a checkpoint typically becomes final after two consecutive epochs of sufficient votes, so finality takes roughly 13 minutes. Cardano, by contrast, uses five-day epochs to schedule stake-pool block production and pay out staking rewards, and Solana's epochs run about two days, governing when stake changes take effect.

A common misconception is that "epoch" means the same duration everywhere; it is purely protocol-specific, ranging from minutes to days, so an "epoch" quoted without naming the chain is meaningless. For everyday users, epochs mostly matter for staking mechanics: delegating, undelegating, or reward accrual often only takes effect at the next epoch boundary, which explains why a stake change can show as "pending" for hours or days after the transaction itself confirmed instantly.