Keeping track of time on Mars is very complicated

You could use a ‘sol’, like Mark Watney did…

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The time slip is fine(ish) when the Mars colony consists of

  • up to 20 or 30-odd folks
  • who are all in one physical location and
  • who are critically connected to Earth for command and control purposes and
  • whose mission is of relatively short or defined duration.

The Apollo missions are a good analogue here - using Houston time (or whatever time they used) even though they were on the Moon made a lot of pragmatic sense.

But it fails abysmally as soon as any of those conditions start to break down.

Reminds me of the most horrifying paragraph ever written in science fiction:

“And there is the council meeting. I haven’t been to a council meeting in years. They hold them in the Commune cafeteria at the long hour on Thursday nights. I don’t know who decided that since the martian day is thirty-seven minutes and twenty three seconds longer than the earth day we should have the hour from eight to nine p.m. last one hour thirty-seven minutes and twenty-three seconds. If we’re going to have a long hour I’d rather have it in the morning. But it’s a bureaucrat’s dream, an hour and thirty-seven minutes to have an hour meeting.”

  • Maureen McHugh, “China Mountain Zhang”

The length of those divisions can also just be rounded to the nearest integer number of SI seconds, with leap seconds inserted as necessary to keep it synced up with the sun, just as we do on Earth.

Hate to break it to you, but UTC is very much Earth-specific even when it’s just represented as a count of seconds since an arbitrary epoch. UTC (and the standard Unix timestamp which is based on it) has leap seconds applied to keep it synchronized with the rotation of Earth.

Mars time would need to be based on its own timebase, probably based off TAI just as UTC is but with leap seconds to synchronize to the rotation of Mars rather than Earth.

Not sure even that would be sufficient, I assume relativistic effects probably add up to pretty significant time slip between atomic clocks on Earth and Mars, so if you want to keep time in a way that lets you synchronize between both planets you’ve got to take that into account too.

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Time is an illusion; lunchtime doubly so.

Douglas Adams


Metric time in 10… 9… 8…


If the world somehow ever moved to metric time, the US would probably shift to Julian time, just out of spite.


At least at the outset, UTC will have to be used in space, and on the Martian surface because it is the basis of all operations on Earth and operations extending from Earth. In the longer term a solar system specific timebase will have to be established but I suspect it will be very similar to UTC.


…and the elliptical mars orbit centered on the sun, instead of having the sun at one of the foci. dying here

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Leap seconds are already so problematic for computers on Earth that there’s sometimes talk of moving away from UTC as the timebase to something without leap seconds. If it causes those headaches on Earth (where keeping it synchronized with terrestrial days is arguably somewhat useful) I don’t see why anyone would put up with that headache on Mars.

Current interplanetary operations use mission-specific clocks, usually based on local solar time.

The proposed MSD (Mars Sol Date) is derived from TT (Terrestrial Time), not UTC. TT is still an Earth-based atomic time scale but does not make any effort to synchronize with Earth’s rotation (UTC is derived from TT via TAI, offset by the TAI epoch and an integer number of leap seconds which is updated periodically).


Won’t there be relativistic effects too?

Mars dwellers will experience time faster because of the reduced gravity there.

The real question is, would you have to do The Time Warp differently on Mars.


I can think of worse.

You could have the ayn-cap’s dream. Distribute the extra minutes during the work day, and only the work day. Everyone unfortunate enough to not be working night shifts will work for longer without getting extra pay.

Red Mars fails on three points

  1. There are 101 people (Later referred to as The First Hundred. One is a stowaway)
  2. They are all in one place, but
  3. One of the First Hundred persuades most of the rest that they shouldn’t be doing what Earth tells them just because they are Earth.
  4. They are there to colonise Mars

Be careful on Deimos. That jump to the left may be the last jump you make.


We can redefine the Epoch time to be seconds since the Big Bang.

I remember having problems with a system way back in ancient times when someone born in the '60s tried to enter their birthday.

The crazy part is with just a 64 bit timestamp this is actually possible.

Assume the Big Bang happened 13.8 billion years ago, that’s 4.36E17 seconds ago. A 64 bit unsigned integer (no need to care about time before the Big Bang) holds values up to 1.844E19. This system would hold up till the year 570,742,046,090. At that point they would have a big Y570B problem to deal with, but that’s a problem I’m willing to leave to future generations to fix.

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Yeah - I read the Mars trilogy many moons ago, and that’s kind of what I was getting at. Earth time would have worked for Boone’s(?) first (prequel) mission, and maybe for a while for the first 100, but not for long given the need to maintain round-the-clock watchkeeping.

And that’s even ignoring the issues raised upthread about computer networks - how do logs work when 40mins of each day is just 00:00:00?

Time in any not-Terrestrial locale will be synchronized with Earthly time because unaltered humans will live in enclosed environments, in caverns and tunnels and submerged bubbles, not on a toxic surface. How often do nuke sub crews need to know the time on the ocean’s surface above them?

Even cyborged or other altered humans on Mars, Mercury, Ganymede etc will find it handy to observe UTC if they wish to deal with vanilla humanity.

Mars time vs Earth time will only become an issue when the Martian surface is terraformed or humans are re-engineered to survive on the raw surface. In which case, we may have technology to slow the Martian rotation to match Earth’s.

If there’s one thing that really sets me off it’s this kind of short-term planning.