#!/usr/bin/env python3

import threading
import time


class TimeChanger(threading.Thread):
    def run(self):
        while True:
            time.sleep(1.5)
            t = time.clock_gettime(time.CLOCK_REALTIME)
            time.clock_settime(time.CLOCK_REALTIME, t - 0.4)


c = threading.Condition()
c.acquire()

time_changer = TimeChanger()
time_changer.start()

while True:
    t1 = time.monotonic()
    c.wait(timeout=2)
    t2 = time.monotonic()
    print(f'Took {t2-t1:.3f} s')