java.time · java.base · since Java 1.8

Clock

declaration

public abstract class Clock implements InstantSource

An injectable time source: fixed, offset, or system clocks. Passing a Clock instead of calling now() makes time-dependent logic deterministic under test.

Key methods

`static Clock systemUTC() / systemDefaultZone()`	Production clocks.
`static Clock fixed(Instant fixed, ZoneId zone)`	Frozen time for tests.
`Instant instant()`	The current reading.