What time is it on Mars?

Right now the time at Mars' prime meridian (Coordinated Mars Time) is shown below, with the local time at the rover landing sites. A day on Mars, called a sol, lasts 24 hours 39 minutes 35 seconds, so Mars clocks slowly drift against Earth clocks, by about 40 minutes a day.

How Mars time works

Mars spins once every 24 hours 37 minutes relative to the stars, and its solar day, the sol, is 24 hours 39 minutes 35.244 seconds. Mission teams don't stretch the hour: they keep a normal-looking 24-hour clock in which each "Mars second" is about 2.7% longer than an Earth second. That way noon on the clock is always roughly when the Sun is highest over the rover.

Coordinated Mars Time (MTC) is the Mars equivalent of UTC: the mean solar time at Mars' prime meridian, which runs through the small crater Airy-0. The Mars Sol Date counts sols since 29 December 1873, a date chosen so the count stays positive for the telescope era. This page uses the same formula as NASA's Mars24 program (Allison and McEwen, 2000), corrected by an internet time check.

Living on Mars time

Rover teams on Earth work on "Mars time" for the first months of a mission, so their shift starts 40 minutes later every day. Within weeks they are starting work in the middle of the Earth night. Engineers have worn custom watches that run slow to keep up, and families learn to plan around a day that never stays put. A Mars year lasts 668.6 sols, or 687 Earth days.

How long does a message take to reach Mars?

Radio signals travel at the speed of light, and Mars is between about 55 and 400 million km away depending on where both planets are in their orbits. A message takes from about 3 minutes to more than 22 minutes one way, which is why rovers drive themselves and no one on Earth can steer them live. More in how NASA keeps time and how long it takes to reach the Moon.