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Understanding Time in Blockchains

In traditional computer systems, time is relatively straightforward, with a reliance on the system clock. However, in the world of blockchains, time is a unique and critical concept. Blockchains need to maintain a shared understanding of time across all participants, and this introduces some complexities. Here's how time is managed in blockchains:

Rounds​

Rounds refer to the cyclic or sequential stages of consensus protocols, particularly in proof-of-stake (PoS) and delegated proof-of-stake (DPoS) blockchains. Each blockchain has it's own length of rounds:

  • MultiversX - 6 seconds;
  • Ethereum - 12 seconds;
  • Solana - 0.4 seconds;
  • Cardano - 5 seconds;
  • NEAR - 1 second;

A round is a time limit to execute a batch of transactions.

Blocks​

Every round a new block is being proposed. That proposal can succeed or not. In case of success, a block is added to the blockchain history. The missed blocks are due to not reaching consensus and are usually under 5%.

NOTE

For MultiversX case, every 6 seconds starts new round, but not necessarly a new block gets notarized.

Epochs​

This is another time measurement and it's used for larger periods of time (just like minutes, hours, years, decades, etc.).

Each blockchain has it's own length of epochs:

  • MultiversX - 14.400 rounds (24 hours);
  • Ethereum - 30.000 rounds (100 hours);
  • Solana - 432.000 rounds (48 hours);
  • Cardano - 432.000 rounds (5 days);
  • NEAR - 43.200 rounds (12 hours).

Block Timestamps​

Blockchains organize transactions into blocks, and each block has a timestamp. This timestamp is crucial for several reasons:

  1. Order of Transactions: The timestamp helps order transactions within a block. Transactions are grouped together and processed in the order in which they are added to a block. This ensures that everyone has a consistent view of the transaction history.

  2. Difficulty Adjustment: Some blockchains, like Bitcoin, use the block timestamp to adjust the difficulty of the proof-of-work (PoW) algorithm. This keeps the block generation rate relatively constant, regardless of the total network hash rate.

  3. Block Validity: Block timestamps are used to determine whether a block is valid. If the timestamp of a new block is too far in the future or past, it can be considered invalid.

Practice​

Check MultiversX Explorer and Ethereum Explorer and see how (almost) at every 6, respectively 12 seconds a new block appears.