The nature of spacetime - Cosmos is fun to a Martian if an astronaut is moving

Time, blue and red clock By Cleonis - Cleonis, CC BY-SA 2.5, Link Sometimes they say time flies when you're having fun, meaning, time seems to pass quicker when one is enjoying oneself. From the local frame of reference (the blue clock), the relatively accelerated red clock moves slower, while the blue clock moves faster considering the red clock and the same local frame of reference.