https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Temporal/ZonedDateTime/epochNanoseconds
Temporal.ZonedDateTime.prototype.epochNanoseconds - JavaScript | MDN
The epochNanoseconds accessor property of Temporal.ZonedDateTime instances returns a BigInt representing the number of nanoseconds elapsed since the Unix epoch...
temporalzoneddatetimeprototypejavascriptmdn