Wraps Jest's built-in modern fake-timers (built on @sinonjs/fake-timers since Jest 27): jest.useFakeTimers(), jest.setSystemTime(), jest.advanceTimersByTime(), jest.runAllTimers(), and jest.useRealTimers() for selective restoration. Use when testing JS/TS code in Jest where setTimeout / setInterval / Date / Date.now need deterministic control.