Time concepts#
Epochs#
The Concordium blockchain divides time into epochs.
When considering rewards and other validation-related concepts, the concept of an epoch is used as a unit of time that defines a period in which the set of current validators and stakes are fixed. Epochs have a duration of 1 hour and the duration is fixed at the genesis block. Each epoch has a nominal ending, and when a block is finalized after this nominal ending, epoch transition occurs.
Rounds#
Epochs are subdivided into rounds. In each round either a block is produced by the elected leader and validated by (2/3 of) the other validators, or a imeout is produced if the timeout time is reached before a block and its quorum certificate are produced. In the case of a timeout, a timeout certificate is produced for the block. The timeout time for the next round may shrink or grow depending on whether a block was finalized or a timeout occurred in the previous round. Using consensus protocol, a validator has to add the new block after the block from the previous round, unless a timeout occurred in the previous round, in which case they can add their block to an older round. The list of lottery winners that are elected to be the leader for every round in that epoch is established at the beginning of the epoch.
Pay day#
A pay day is the point at which new CCDs are minted and rewards are distributed to validators and delegators. The stakes of validators and delegators are updated each pay day (but the changes for each pay day are fixed one epoch before). Pay day is thus when new validators begin producing blocks, and updates to delegation and validation take effect. Pay day is every 24 hours (i.e., 24 epochs) at approximately 09:00 UTC on Mainnet and approximately 12:00 UTC on Testnet.
Cool-down period#
In the case of decreasing stake or removing delegation or validation there is a cool-down period of three weeks during which the unstaked funds are frozen. For example, if you decrease a valiator’s stake, the stake will be decreased at the first pay day but the funds will not be released to your disposable balance until after the cool-down period ends.
