Summary

When computing the time between java.time.Instants using MILLIS.between(t1, t2) or MICROS.between(t1, t2) or t1.until(t2, MILLIS) or t1.until(t2, MICROS) the difference may be incorrect.

Problem

The implementation of java.time.Instant.until(Instant t, TemporalUnit unit) is specialized for computing the number of milliseconds or microseconds between two Instants. The representation of an Instant is the number of seconds and the number of nanoseconds. The implementation computing the number of units between, as of JDK 18, did not propagate carry and borrow between seconds and nanoseconds when computing milliseconds and microseconds between Instants.

The computations are correct in cases where the difference in nanoseconds is whole milliseconds or microseconds respectively.

Solution

In the cases where the difference in the number of seconds is negative and the difference in the difference of nano-seconds is positive and the case where the difference in seconds is positive and the difference in nano-seconds is negative the difference in the number of seconds is updated.

Specification

There is no change to the specification, the implementation is updated to correctly return the number of milliseconds and microseconds between the instants.