Epoch microseconds

[ptomato]

Bringing microseconds back!

Advantages:

I learned today that Postgres uses 6 decimals of precision for its timestamps and elapsed times. Temporal.Duration supports microseconds just fine, but for epoch microseconds in Instant and ZonedDateTime you have to use a slightly annoying calculation: tc39/proposal-temporal#2849 (comment)

Concerns:

Feature was previously removed for space concerns. When adding new features in a follow-up proposal we have to prioritize what to add.

Prior art:

Previously in Temporal, we had Temporal.Instant.fromEpochMicroseconds(), Instant.prototype.epochMicroseconds, Temporal.ZonedDateTime.prototype.epochMicroseconds. They were removed in 2024 (tc39/proposal-temporal#2849) as part of cutting the size of Temporal to fit on resource-constrained devices.

Constraints / corner cases:

N/A

[ptomato]

cc @EricLendvai - thanks for the feedback!