Epochs as part of the current Babylon version of the Radix Public Network are targeted to last 5 minutes. The number of "rounds" within an epoch is adjusted dynamically by the Radix Protocol in order to achieve this There is a hard-coded minimum of 500 rounds, and a maximum number of 3000 rounds in an epoch. See the Radix Tech Docs for more.
Further reading:
- What’s an epoch?
- How do XRD emissions work?
- How XRD staking emissions rewards are calculated - general
- What are “rounds” and what does “rounds per second” mean?