Supposedly we human are able to terraformed Mars decades from now, then in few hundred years able to enhance our genes to be more adaptable to live on harsh conditions, creating space colonies and starting to live on moon, Jupiter's moon, all the way to Saturn. Supposedly we also invented FTL travel between our colonies, and planets in solar system.

As dates and years will become very relative, it would be a disaster in daily basis to scheduling for 3D video call meeting, or planning some events if human still count days and years like we do now.

So what will be the best way as the universal standard time keeping in this situation?

It's more about the substitute of days/months/and years count that we used now based on earth rotation and revolution, what's the other alternatives that can be socially accepted that's not linked on just one planet movement? Sun movement can be accepted as we deal with just one solar system.

(Hours/second would easily solve able using whatever precise time counting device that we will have in the future.)

As @cort Ammon has showed the linked question in here. I've revised the question, since I've checked and still not found the answer.

Thank You

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    $\begingroup$ Why is having a unique time and date for every body (kind of like time zones) not a possibility? Converting this when going someplace else should be pretty easy as computers are still available. If it doesn't apply to one particular situation, something like earth standard time would be straight forward. Also please note that a 3d video call from Saturn to Earth would look, well, a tiny bit laggy $\endgroup$ – Raditz_35 Jun 14 '17 at 14:26
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    $\begingroup$ Well, I'm making a galaxy with its own time system, because the time system we use only logically makes any sense if you're on earth. Since it's still in this galaxy, I think seconds, minutes, and hours could still be "universal" time measurements. However, the "day, week, month, and year" measurements would only be useful culturally. If I got to decide, I'd have time increments higher than an hour that apply to all planets. Like a "powour" (random measurement name) could be 60 hours, and a "len" could be 60 powours. Larger time increments for everyone to use. $\endgroup$ – Iter Jun 14 '17 at 14:33
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    $\begingroup$ @StephenDiMarco If we have FTL spaceships, the best way actually might be to send usb sticks (or something) with videos through the solar system to have something like that call. Now I want to build THAT world $\endgroup$ – Raditz_35 Jun 14 '17 at 14:34
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    $\begingroup$ Ran out of characters, but going by that, you could have a "galactic time" which is kept constant throughout the galaxy, likely with an atmoic clock (and some redundant clocks to be safe). So the time is constantly being given to each planet, and while they have their own planetary times, the galactic time allows for communication interplanetarily. $\endgroup$ – Iter Jun 14 '17 at 14:35
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    $\begingroup$ How is this different from “Assuming that a majority of Humans come to live offworld, what is likely to be the most widely agreed upon way of time-keeping?” ? I still don’t see what’s different here. And aren't the people answering just duplicating what's already been said? $\endgroup$ – JDługosz Jun 15 '17 at 3:02

I think people, for many centuries, would just refer to Coordinated Universal Time, or UTC, similar to Greenwich Mean Time.

It won't make a difference that it is Earth Based: There is no standard that will make sense on all planets, so it might as well make sense on one, and the natural candidate for that is Earth.

Locally, it would make sense to use orbital fractions: The planet rotation, from one high noon to the next, is 0% to 100%. On earth that is 24 hours, and 1% is 14.40 minutes; but universally, 50% is 'midnight' and 0% or 100% is "high noon". However, that said, our "seconds" and "minutes" and "hours" would probably continue in use; they are arbitrary divisions that correspond to no natural phenomenon.

The other orbital fraction is the percent of distance around the sun, measured from perhaps the closest approach: Again 0% is probably the height of 'summer' and 50% the dead of 'winter'. On earth, 1% is 3.65 days, and 2% is about a week.

This gives them a somewhat consistent frame of reference for local time of day and year. To get precise and talk about hours, minutes and seconds for interplanetary transactions or interactions, everybody does what we already do: Refer to UTC +/- whatever.

I routinely have meetings with people that reside in other countries, and conference calls that may involve people in six countries. Sometimes that means I have to be up and online at 3:00 AM, my time, or 9:00 PM, but everybody manages whatever their job requires.

And certainly in a high tech future; computers will take care of all those local-to-global conversions for us very easily. For example, a voice command and exchange like:

"I have a conference call with the build team at UTC plus eight next Earth Thursday, what time will that be?"

Computer: "55% of a rotation, in three rotations."

"Shit. Alert me before dinner that day, and I need a wake up call 90 minutes before the call."


Generally speaking, you wont find a single answer for how to manage cyclical measurements of time on a galactic scale or even a solar system scale. The reason is simple: cyclical time systems exist because they are convenient. Whatever system you come up with will be deeply entwined with the particulars of how your culture has evolved over the millions of years it took to colonize the galaxy, or over the hundreds of years it took to colonize the solar system.

We divide our time into days because it is convenient. We happen to have a physical reason to do so. There is a pattern of light and dark that occurs on a specific period, and it turns out that period is rather important for a species that is better adapted to light than dark. So the first question you would have is: is the cycle of light and dark important on my planet. If it is, then the concept of a day will be important, no matter how hard you try to force people into a uniform standard.

Generally I would expect a uniform standard to go the way of TAI or ECB or Unix Timestamps -- measuring seconds since an epoch. You could change the unit if seconds are too Earth-elitist for you, but what matters is that you're measuring on a linear system that counts upwards from 0 without ever cycling. Why? Because once you've picked a single cycle (in our case, the second), there's really no reason to pick a larger cycle unless there's a physical or social reason.

So you should ask yourself, "what is the heartbeat of my empire?" What pulse shudders through it? Perhaps all financial transactions are handled all at once every 1000s. That heartbeat would naturally cause cycles to form. I'd start talking about things occurring in "4 transaction cycles" naturally.

One source of cycles you will find is conjunctions of two dissimilar cycles. The Inca had two calendars: a ritual calendar that's 260 days long and a 365 day solar calendar. This is similar to what would happen if you had two planets trying to treat their own year as a cycle. The result is that there was a 52 year cycle marked by the point where the two calendars line up. These calendars were, of course, a matter of convenience. The crops had to be planted based on a solar calendar, while the ritual calendar supported a 13 day ritual cycle that the society created.

Failing to find a meaningful convenient cycle, its likely humans will just fall back on the metric system. Divide time into 100s and 10,000s cycles and leave it at that. Any meaningful cycle would likely override this, but if your culture truly doesn't have a dominant cycle to build from, our love of base 10 will show through. It shows through today: I can say that I wrote this answer in '17, and everybody knows I am referring to a date on a 100 year cycle. What's 100 years? It's arbitrary, but it's a power of 10, which makes calculating it from the long count (2017 years AD) easy.


I'd suggest using Unix time, with extra specification that it is adjusted by time that passed on Earth. It already don't try to stay in sync with slowing rotations of Earth, so it would be quite practical and neutral. Already were discussed issues related to slightly longer day on Mars. Some people suggested trying to keep track with normal Earth time, but it somewhat neglects the "minor" issue of time zones on Earth. (yeah, EU colony can keep GMT, while US colony would use one of US time zones...)

Space bases of course could keep Earth days, but they would almost for sure need people working in shifts, so it would not matter so much. Especially when thanks to FTL one could suffer from epic equivalent of jet lag.


As someone else on here noted, the day/night cycle is important to people and not likely to be ignored just because there are other people are on a different planet with a different day/night cycle. Just like time zones on Earth: Yes, we all know that when it's noon here in Michigan, U.S., it is not noon in Tokyo, Japan. But that doesn't stop us from still getting lunch around our local noon. It's natural and convenient.

Anyway, I think that just like with time zones, people would eventually agree on some standard way to keep time, which they would then convert to and from local time as necessary.

Others have mentioned using something like Unix time, where you count seconds continuously from some convenient starting point. In the case of Unix, I think it starts from January 1, 1970, midnight UTC. So in Unix time, January 1, 2017 is somewhere around 1,451,649,600. That is, it's that many seconds past the start of the epoch. (If I bungled that calculation, sorry, but not important to the point.) Computers have functions to convert a Unix "number of seconds" to a date and time on the Gregorian calendar. You have to specify what time zone to get the correct time, and the time you get will be different for different time zones. The computer can just as easily convert to the traditional Chinese calendar or the Jewish calendar or any other calendar out there.

Maybe for local matters, people would use local time. But people who routinely talked to folks on other planets might use such a universal standard. A big catch is that ten digit numbers are hard to comprehend and work with in your head. If it's 1,532,203,201 now and you say you want to hold a meeting on 1,532,845,282, how far away is that? It's hard to grasp quickly and intuitively.

My suggestion: Deal with it with a combination of metric system prefixes and omitting high order digits when they're irrelevant.

That is, today someone might say, "Let's get together in two days to discuss this." I doubt people will ever routinely say, "Hey, let's get together in 172,800 seconds." But they well might say, "Let's get together in 170 kiloseconds". Or instead of, "This happened on January 1, 2017", I don't think people will say, "This happened at 1,451,649,600." But they might say, "This happened at 1451 megaseconds."

Today, for small time intervals we often don't specify the high-order intervals. For example, if someone says, "Let's have lunch at 11:30", I assume they mean 11:30 today. If it's June 14, 2017, no one says, "Let's have lunch on June 14, 2017 at 11:30." People could do the same thing with Unix time. If it's presently 1,542,320,822 and you say, "Let's have lunch at 390 kiloseconds, the other person would understand you to mean 1,542,390,000. That is, take the leading part higher than kiloseconds from the present time, and then replace the kiloseconds with the value given.

Implied in this is that people would come to think of time in decimal multiples of 1 second rather than minutes, hours, day, months, and years. Instead of saying, "A typical work day is 8 hours" we'd say "A typical work day is 29 kiloseconds." Instead of saying, "We got married 5 years ago" you'd say "We got married 160 megaseconds ago". Etc. And people would quickly learn to round to the powers of ten, not to whatever number of seconds the old units came out. Like where today someone might say, "This job will take several days", people using this system would NOT say, "This job will take several multiples of 86,400 seconds." They'd say, "This job will take hundreds of kiloseconds."

Of course they wouldn't necessarily use seconds since January 1, 1970 in Greenwich, England, Earth. They could choose any convenient starting point and any convenient size unit of time. Something larger than a second would probably be more convenient, and then use fractions for smaller units. Like maybe you'd use a base unit of time roughly equal to an Earth day. (Not saying it would be based on any Earth cycle, just that order of magnitude.) Then, supposing you called this unit, I don't know, a "fwac", you might say "This project will be completed in 300 fwacs", meaning not quite an Earth year from now, or "Let's call a meeting for 6 decifwacs", meaning, the time that is 0.6 fwacs into the current (whole) fwac.

Pedantic astronomers would probably insist that the size of the unit and the starting point must have something to do with the rotation of the galaxy around the core, or physicists might think it's a great idea to base it on the time it takes for some selected isotope to decay. They'd probably win, but this would be silly and pointless. It would make more sense to just pick values that are convenient for human beings to work with.

  • $\begingroup$ Oh, and let me add: I'm confidant that if people adapted such a system, they'd quickly get comfortable with the units and have a "feel" for how big they are. Just like on Earth today, someone who has never used the metric system might well be confused about how big a "kilogram" is. Is that an amount I can easily lift? The weight of a house? Etc. But once you've used metric for a while you get a good intuitive feel for each of the units. Likewise in this system people would presumably get to comfortably know that 5 centifwacs is about how much time I take for lunch and that someone who is ... $\endgroup$ – Jay Jun 14 '17 at 19:51
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    $\begingroup$ ... 7 kilofwacs old is just becoming an adult. Etc. $\endgroup$ – Jay Jun 14 '17 at 19:51
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    $\begingroup$ physicists might think it's a great idea to base it on the time it takes for some selected isotope to decay the reason is that's how atomic clocks work. That ad hoc definition replaces the arbitrary one of 1/86400th of a day. It makes sense to tailor the definition of your basic unit of time around your timekeeping device of choice. $\endgroup$ – AmiralPatate Jun 15 '17 at 10:20

It is very likely that there will be a dual-system.

Something completely artificial, but precise, most likely a Real number (floating-point) like "stardate" (number of days, fractional; roughly equivalent to one wake/sleep cycle) or "unix" (number of seconds, fractional in recent incarnations; as a short period, close to a "least common" unit). In this things like months or years bear no meaning and probably would be dropped.

Something local, bearing resemblance with the planet at hand; there days and longer units linked to seasons would be needed. Absolute precision is not a requirement, but long term stability is.


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