Solana Rust onchains program have access to

solana_program::clock::Clock::get()?.unix_timestamp

which is seconds from epoch (midnight Jan 1st 1970 GMT) but has a significant drift from any real-world time-zone as a product of Solana's slowdowns over time. Many contracts factor in this unix timestamp when calculating reward amounts (notably Step Finance and therefore Gem Farm which reuses the logic). How can I reconstruct this Solana unix timestamp on the front-end in JavaScript without requiring any transaction / wallet signature? Calls to a Solana node RPC are fine.