On July 30, 2015, the very first Ethereum block was added to the blockchain. From that moment, anyone in the world could start building on Ethereum.
Why it mattered
Before Ethereum, blockchains were mainly used to transfer value. Ethereum introduced programmable smart contracts: code that runs automatically on a blockchain.
For the first time, developers could build decentralised applications directly on a blockchain, without relying on a central company.
Why it still matters today
Decentralised exchanges and lending protocols build on the smart contract model that Ethereum pioneered.
Nearly every time you swap a token, borrow crypto or trade on-chain today, you're benefiting from the smart contract model that Ethereum brought into the mainstream.