The UNI token airdrop was held on September 1, 2020, at 12:00 am UTC. Anyone who has used Uniswap before this date is eligible for the airdrop.
This is the only Uniswap airdrop that is affiliated with the Uniswap Protocol.
How to check if you are eligible for the UNI Token Airdrop:
Connect your wallet to app.uniswap.org
If your wallet is eligible you will see an “UNI has arrived” popup in the Uniswap web app.
Click on “Claim your UNI tokens” and approve the transaction.
Read more about the UNI token launch and airdrop in this blog post.