What we care about is getting all the nodes to agree on what order the transactions occurred (aka "Proof of History"). And Solana's goal is to reach that agreement quickly, that's why they call themselves the most performant blockchain.
So how does Solana introduce a concept of "time" without relying on a central authority?
Solana uses a "hash that runs over itself continuously with the previous output used as the next input". Performing a hash over and over again takes some time. Then, someone can quickly verify that this "time" has occurred. The verification of the hashes can be parallelized on a GPU, which makes the verification extremely quick.
https://medium.com/solana-labs/proof-of-history-a-clock-for-...
