The April 14 hardfork date is estimated and subject to block time variability.
Before being deployed on the mainnet, Berlin will first be deployed onto testnets.
The complete roll-out schedule is as follows (these dates are estimated):
On March 10, 2021, Ropsten will fork at block 9,812,189.
On March 17, 2021, Goerli will fork at 4,460,644.
On March 24, 2021, Rinkeby will fork at 8,290,928.
And finally on April 14, 2021, the Ethereum mainnet will fork to Berlin at block 12,244,000.
If you are a node operator, you will need to update your client prior to roll out. Upgrading several days in advance is recommended since the expected date and block number are subject to change based on block time variability.
The Ethereum client versions that support the Berlin upgrade are available now.
Official links are provided by the Ethereum dev team at the following link.