During betanet, we expect epochs of 1-2 days for testing purposes.
For mainnet, epochs are based on a number of blocks, rather than a fixed “wall clock” time, but they are likely to last approximately two weeks.
It should be noted that the trigger for a new epoch on the Olympia mainnet is not elapsed time, but by a set number of elapsed blocks. However the result should be approximately two weeks per epoch.
Please see here within Blockchain & DeFi Basics for what an epoch is.