About unix time

Unix time counts seconds since 00:00:00 UTC on January 1, 1970, ignoring leap seconds. It's the standard way computers store moments in time because it's a single number — easy to compare, sort, and do math on — with the timezone applied only when a human needs to read it.

Different systems use different precision: ten digits is seconds, thirteen is milliseconds (what JavaScript's Date.now() returns), sixteen is microseconds. This tool detects the unit from the number of digits and tells you which one it assumed.

The famous “year 2038 problem” only affects systems that store unix time as a signed 32-bit integer, which overflows on January 19, 2038. Anything using 64-bit time — including JavaScript — is fine for the next few hundred billion years.