In regards to fantasy dates, they're usually set somewhere between 100 - 9000 W.E (Whatever), but rarely exceed 10,000. Is there a reason for this besides being more aesthetically pleasing?

More importantly, what happens when the date becomes too long? It seems counter productive to be writing the year as '300,000,000 BC/AD" So what would happen if it ever came to that?

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    $\begingroup$ We wrote `95 not so long ago. What's wrong with continuing doing just that? $\endgroup$
    – Mołot
    Commented May 22, 2017 at 12:00
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    $\begingroup$ You could do the same we do with other long numbers: use a different unit. Instead of BC you could use MBC for Mega-BC and abbreviate your 300,000,000 BC to 300 MBC. This example is very crude, but it depends on what events are important to your civilization. Another version would be to choose a different starting point every 10,000 years or so. "Time of the first empire", "Time of the second King", "Time of the [xyz invention]", ... $\endgroup$
    – Secespitus
    Commented May 22, 2017 at 12:05
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    $\begingroup$ The term Y10K has already been coined for the common bug of restricting year fields to 4 digits. Time now to switch to ISO-8601 and write dates as 2017-05-22; that format continues to work past 9999CE $\endgroup$
    – MSalters
    Commented May 22, 2017 at 14:19
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    $\begingroup$ Noteworthy counterexample: Frank Herbert's Dune. The rule of House Corrino lasts over ten thousand years which places the book in the year 10193 AG and following. $\endgroup$
    – Ghanima
    Commented May 22, 2017 at 17:23
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    $\begingroup$ Of course, all dates are relative to some "anchor" event. As soon as a better anchor occurs, date reckoning will be "reset" to be relative to the new anchor. $\endgroup$
    – MPW
    Commented May 23, 2017 at 2:04

9 Answers 9


Fantasy and real world dates rarely pass 10.000 because cultures don't tend to survive that long. Date systems generally start with a significant event as 0: rise of a king, birth of a prophet, founding of an empire, solar eclipse etc.

Between those moments and the fall is rarely more then a thousand years, two thousand perhaps. I figure that if the system becames too broken we would just adopt a new one. The gregorian calendar wasn't the first one we used.

Only recently we have been even contemplating time periods longer than thousands of years ago. Having a need for such a system implies an advanced civilization. One who undoubtedly knows many date keeping systems. If we ever spread across the stars a central date keeping system becomes pretty meaningless too. Days and months vary per planet, traveling near lightspeed causes all sorts of weird effects on aging etc.

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    $\begingroup$ Well, it's easy to say since writing itself is only about 6k years old. We tend to forget about most humans after 6k years then because we do not have writing for that long? I'd be surprised if the story of Giglamesh was lost in the next 5k years or so. $\endgroup$
    – Raditz_35
    Commented May 22, 2017 at 12:25
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    $\begingroup$ "Between those moments and the fall is rarely more then a thousand years, two thousand perhaps." here comes the jinx... $\endgroup$
    – frarugi87
    Commented May 22, 2017 at 13:11
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    $\begingroup$ Actually significant events were usually assigned as year 1: 1 AUC was the (traditional) founding of Rome, not 0 AUC. As for our current dating system, we've only been using it for 1492 years (since 525), so no worries about us hitting our 2000th year yet. :) $\endgroup$
    – Charles
    Commented May 22, 2017 at 23:29
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    $\begingroup$ @Charles, think of the number line: the event is assigned zero. The year that started with that event is the first year. $\endgroup$
    – n0rd
    Commented May 23, 2017 at 5:51
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    $\begingroup$ "rarely more then a thousand years, two thousand perhaps" - In the Hebrew calendar, today is the 27th Iyar 5777, so they are already more than have way to that magic 10,000 year line. $\endgroup$
    – Dubu
    Commented May 23, 2017 at 9:18

Take a look at how real-world calendars have dealt with this.

The infamous Mayan calendar, for example, counted days from a start point in 3114 BCE, using 5 periods. Each period counted from 0 to 19 then rolled over back to 0 (except the second-shorted period, which had a period of 18). Thus each period represented a set number of days.

August 12th, 3114 BCE was  
August 13th, 3114 BCE was  
September 1, 3114 BCE was  
January 1st,    1 CE  was  
   May 22nd, 2017 CE   is

Using this system the Maya could track dates from the year 3114 BCE up to 4772 CE with ease. You can use something similar to track large expanses of time in your world, especially if you're willing to use periods greater than 20.

For example, we westerners might like to use a structure of Year.Month.Week.Day, especially if we were willing to make our months a little more sensible and set them all to 28 days long (1 lunar month). This year would begin at 2017.01.01.01. We don't generally use 0s in our time counts, so we're starting at 1 for each period. Today's date (as I type this) would be 2017.05.01.01

To make this truly useful to track very large dates, though, we should add a fifth period. I would suggest the Great Year - the time it takes Earth's axis to precess a full 360 degrees. A Great Year lasts about 25,800 years; we could divide that up into 12 periods to represent the signs of the zodiac, giving us a period of 2,150 years per constellation.

Today's date        01.2017.05.01.01  
January 1st, 2200  
January 1st, 10191  04.1591.01.01.01  

If you want to go beyond the year 25,800, you could add yet another counter, to track the Great Years:

January 1st, 426,255: 16.06.555.01.01.01

For common use, of course, you wouldn't need the first two periods - the current year and date would suffice. The full count would only be used in formal settings, similar to how legal documents often spell out the year in full (Nineteen hundred and whatever).

It gets a little convoluted, with all the different values being used, but it can track some pretty darn high dates with great precision.

Also, there is an excellent chance that I've fouled up the numbers somewhere up there - I'm a logical guy, but dyscalculia is a thing. Feel free to edit and correct any numbers I've screwed up.

  • $\begingroup$ Year/Week/Day is used in a few strange cases. Usually, it's because of a system that releases data weekly, and so they number the by YYWW or YYYYWW ... Day is then a discriminator within the file (sometimes as Y/M/D, sometimes as Y/DOY, or Y/W/DOW) $\endgroup$
    – Joe
    Commented May 23, 2017 at 23:33
  • $\begingroup$ Huge problem with your system is that there are no full weeks or full 28-day months in year causing "precession" of calendar year versus astronomical one. It's not a good idea for region to have summer in June or January depending which year it is. $\endgroup$
    – M i ech
    Commented May 24, 2017 at 1:46
  • $\begingroup$ @Miech Thanks for reminding me, I meant to include a side note on that - you can handle it a few ways, like having one or two months with extra days, or by having a few days per year set aside as being 'outside' the calendar. $\endgroup$
    – Werrf
    Commented May 24, 2017 at 1:49
  • $\begingroup$ @Werrf Holiday days "outside" calendar seems to be a common trope in fantasy. Did anything like that actually occur in history? $\endgroup$
    – M i ech
    Commented May 24, 2017 at 1:55
  • $\begingroup$ And of course, you can always define a new epoch and provide a way of (easily) going from this cycle to that cycle. The unix time stamp is like this - number of seconds since midnight jan 1 1970. Of course, this means we're gonna have a Y2038 problem if we keep using the 32bit number... $\endgroup$
    – ivanivan
    Commented May 24, 2017 at 2:22

This is an interesting problem to tackle because it deals with timescales that most of us are very unfamiliar with. My first recommendation to anyone dealing with such timescales is to read Stephen Baxter's book Manifold Time. It's one of the few books I've have seen which truly grasps just how strange life can get when making sense of how things are in the year 1,000,000,000,000,000,000,000,000,000,000,000,000,000 AD. Yes, that makes 300,000,000 BC/AD look pretty tame by comparison, and yes, Baxter goes much further into the future than that!

There's a few solutions to the issue you describe which have some history. The first key to all of these is that we are really trying to describe a "time point," and we typically want to do so using a number. The second key to this is that the purpose of such dates is communication. Our goal is to convey the concept of the time point to another individual.


Cycles are a very popular approach to dealing with large dates. Instead of counting numbers of days, we count in months, then years. Other cultures, such as the Mayans, had even more exotic cycles.

The fundamental reason cycles work is because the events we care about tend to occur on logarithmic timescales. Consider how many things we care about happening in a day. You might have 5-10 points in the day that matter enough to pay attention to. Now think about a month. Obviously you don't pay that much attention to the 150-300 points in the month corresponding to the 5-10 points every day. That'd drive you bonkers. Instead, you have 5-10 really important things to look forward to in the month, like pay day or someone's birthday. Look at a year. You might have 5-10 major events that you truly care about, like a family vacation or a major release of a product at work.


We currently are living 2000 years after the epoch of our current numbering system for years. This can be inconvenient, so we are known to shorten it to a 2 character year for convenience. As long as we're certain that '05 means 2005 and not 1905, this approach is very effective. Most time points we want to convey are within one lifetime, so we only need 2 digits.

If you think about it, this is really just a special case of the cycles solution above, which only works on cycles of 10 or 100 years (or whatever based numbers your civilization uses).

New Epochs

We're known to invent new epochs from time to time. When we do this, we define a new time point to base everything off of, and do math to convert one time into another. The most famous of these right now is the Unix Timestamp, which counts the number of seconds since Thursday, 1 January 1970 UTC (sans leap seconds). Why was 1970 chosen? Well, there's many reasons but one of the major ones is exactly the issue you describe in the question. If you're counting a number of seconds, that number can get big in a hurry. 32-bit computers could only count to just over 4 billion seconds, so they had to choose a time which meant most times that people in the computer age could care about fit into that window. 1970 fit the bill. Of course, they're running into trouble soon: on 19 January, 2038 03:14:08 GMT, the Unix timestamp will run out!

There is often a meaningful time where an epoch gets specified. Historically, many dates where given in terms of the ruler's reign. You might talk about an event that happened 5 years into the rule of King Henry. In more modern times, we defined a very important epoch for humanity in 1972, when we defined UTC in terms of atomic clocks. Nobody had every defined the second so precisely, so there was no way to determine exactly what the current time was when setting the first atomic clocks. The solution was that we defined a new epoch, such that all clocks would read 0 at that time.

Interestingly enough, we've also used the act of defining new epochs to go the other way. The single most common way dates are measured in the high-precision community is as a Julian date. For example, a major point in timekeeping forked off 2 additional time systems on Julian Date 2443144.5003725 in order to deal with time dilatation effects that had been unexpected until that point. Note that that date number is pretty big. Julian Dates are based off of the number of days since noon on January 1, 4713 BC, on the proleptic Julian calendar. That odd year number, 4713 BC, was chosen intentionally to be far in the past. It was designed to be so far in the past as to occur before any recorded history (as well as being the conjunction of several cycles deemed important at the time).

Measuring from the Present

This is a bit tricky, because it doesn't fit well with the math, but we measure time with respect to the present all the time. We talk about something that happend 3 hours ago, or 4 days ago. This approach has a disadvantage of being only valid at the moment in time where the date was uttered, but sometimes that's enough. We're used to working with a web of relative times.

Brute Force

If brute force doesn't work, you're not using enough. Humans may have trouble with large numbers, but computers don't. If your civilization becomes highly computerized large timestamps become easy to handle.

NTP timestamps are an excellent example. Right now they are 64 bit structures: a 32 bit integer number of seconds which will roll over in 2038 (with the Unix timestamp), and a 32 bit integer number for fractions of a second. However, there is talk of making them 128 bits long. This would be sufficient to measure times as "small as the time it takes for photon to pass an electron," and "large enough to be valid until the universe goes dim."

The key to this is that computers can handle these numbers so well. To a computer, the year 2015 is no more difficult to capture than Julian Date 2457023.5. Our number systems, with its place-based notation grows logarithmically, so each additional digit gives us another 10 fold increase in numbers.

This works great until the energy cost of storing a 128-bit timestamp in memory starts to become important. But for that story, read Steven Baxter's book!

  • $\begingroup$ 2038 rollover is only for 32-bit timestamps that track seconds since 1-1-1970. 64 bits gets us much, much further than that. However, since we want to track much smaller increments than seconds, those 128 bit timestamps may still be worth it. $\endgroup$
    – tucuxi
    Commented May 23, 2017 at 7:47
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    $\begingroup$ @tucuxi I didn't get much into the actual format of the NTP timestamp, but that's exactly what they do. The old timestamp is actually two 32-bit ingegers: a 32-bit seconds since epoch and a 32-bit fraction-of-a-second. The 128 bit timestamp makes both of those parts into 64 bit integers. $\endgroup$
    – Cort Ammon
    Commented May 23, 2017 at 15:03
  • $\begingroup$ You should clarify this distinction - at first reading, it appears that 64 bits will soon not be enough; but Y38K is due to failing 32-bit unix timestamps, and not failing 64-bit NTP ones. I misread it, and I feel clarifying would improve your great answer. $\endgroup$
    – tucuxi
    Commented May 23, 2017 at 16:19
  • $\begingroup$ @tucuxi Edited. It makes the sentence read a bit funny, but it clarifies that issue. $\endgroup$
    – Cort Ammon
    Commented May 23, 2017 at 16:47

It's worth noting that we don't even use full dates (100% of the time) in modern times. Most of the time it's simply 96, 01, 17, etc.

To answer your question, official records could contain the whole year while letters and casual reference would likely refer only to the last two digits. Humans generally don't live beyond double digits, so only referring to the last two digits allows others to understand what is meant.

Alternatively, the solution could be to add letters.

Starting at 10,000 it would be A0000, and the last usable date with that system would be Z9999. This would cover the span of 260,000 years.

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    $\begingroup$ Your last paragraph is very important in my opinion. The OP is talking about "fantasy" in his question. So if you use for example elves in your work they might use the last 3, depending on how old they can get. Long-living aliens might use 4 digits, or humans could start to use 3 digits once people can regularly become older than 100 years. That might be a good thing to keep in mind when designing different species or thinking about the far future of humans. $\endgroup$
    – Secespitus
    Commented May 22, 2017 at 12:37
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    $\begingroup$ Suddenly calendars can be saved in xlsx format $\endgroup$
    – Darren H
    Commented May 22, 2017 at 21:40

Let's assume that science have taken over the world. And they start counting time from the birth of our Sun. So they go with 4,5 bln. But hey, it's ok if you tell time in the billion years event, but when you go to millions you go 4 mln. And thousands? you go 4k. and hundreds? just write 86.

There are events that can't be put in the month/year/century/ bracket. For example the time when dinosaurs walked the earth. You just can't pinpoint "from Monday about 5 o'clock till 5 millions years later Friday around breakfast".

Look at different example. When somebody ask you for time do you answer "first day of the fourth week of the middle month of the second quarter of the seventh year second decade of third millennium" or you just go "4.35"?
After sometime you just stop counting because YOU DO NOT CARE. Even if you are a deathless Emperor on a golden throne you just go with 40K because you don't care about days or months.

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    $\begingroup$ Who cares about calendar when you have the Emperor? Without the Emperor, there is nothing... And we would have no purpose $\endgroup$ Commented May 22, 2017 at 17:29
  • $\begingroup$ I like the fact that you describe how calendar date importance is relevant to the length of life of the sapiens and those around them in the setting $\endgroup$
    – Sarfaraaz
    Commented May 23, 2017 at 9:06
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    $\begingroup$ In the grim darkness of the far future, there are no calendars... $\endgroup$
    – A C
    Commented May 23, 2017 at 20:39
  • $\begingroup$ I disagree with last paragraph. It's 40k part that is irrelevant. Immediate past and immediate future is much more important. Who cares that it's 41st millenium? It's the last year's glorious campaign that is important. Thus out of say 40070, it's 70 that is important, not 40000. $\endgroup$
    – M i ech
    Commented May 24, 2017 at 1:53
  • $\begingroup$ @Miech If you are part of Imperial army then yes. You care for the spare years. Emperor don't as one decade is just a glimpse to him. And this is my point, Imperial army use decades, marines live hundreds of years and Blood Angels thousands. Bjorn can use the 40K dates. $\endgroup$ Commented May 24, 2017 at 9:57

There are a few precedents for solutions to this sort of thing.

The Elder Scrolls series of games uses Eras in its timeline, while Tolkien's Middle Earth uses Ages in its timeline

In both of them, these eras are divided not by a set amount of time but by significant events. In the Elder Scrolls mythology, a few are started by someone founding a dynasty or empire, or even by declaration. Some eras are really long, others are much shorter. With Tolkien, the start of specific Ages seems less clear.

Regardless, this method allows for ease of remembering how long ago something is while not necessarily bogging things down in super-specific definitions. If your story is in the Fifth Era, and you reference something in the First Era, you can tell - without knowing how long any of the eras are - that it was a Long Time Ago.


The Human Era or Holocene Era dates events from an arbitrary date of 10,000 BC so that no historic or recent prehistoric dates have to be counted backward. Thus the current year is 12,017 HE as well as 2017 AD.

The advocates of that calendar see no problems with dates over 10,000.

Astronomers use the Julian Day number, counting the days since January 1, 4713 BC. The current Julian Day number when I write this is 2457893. That is 2,457,893.

According to this the value of the Vulcan Old Date in some Star Trek fiction can equal or exceed 140,005. This may be in Vulcan years or other Vulcan time units.


Possibly people can use two or more different year counts. Perhaps proclamations and rewards for criminals can give the date both as year 25 of the reign of Emperor Alynomern CCXXXV, 10,001st emperor of the Atlantean Empire, and also year 270,025 since the founding of the Empire. Young people may tend to use the regnal years of the current emperor when calculating their ages, while older people have to use the years since the founding of the empire to calculate their ages.

And maybe some people also say the year is 186, counting since the latest war with Lemuria. And perhaps to some people the year is 5,751, counting since the foundation of the dynasty of the present emperor (Alynomern CCXXXV) which is the latest of the recent short lasting dynasties.

And maybe in the introduction you can say that the story begins late in the history of Atlantis, "only" 154,825 years before Atlantis sank under the sea! That will certainly give you enough time for Atlantean sequels.

The story "Out of the Aeons" by H.P.Lovecraft and Hazel Heald, concerns a legend of the lost continent of Mu that is calculated to have happened similarly far back in the past.

It was in the Year of the Red Moon (estimated as B.C. 173,148 by von Junzt) that a human being first dared to breathe defiance against Ghatanothoa and its nameless menace.



With computers, the date will never be too long.

So what if the year is 654,546,534,120,296,145? A computer can easily store and communicate numbers like that. And that far into the future, we could have computers implanted in our brains so we can do complicated arithmetic in our heads, remember everything and communicate as quickly as a wireless data transfer. Whatever problems exist in that year won't include the size of the number.


What date system would be used

If the years got to giant numbers (like the year 3,000,002,017), then a system could be used that writes the last few dates, then specifies how many digits are excluded.

How the date would work

The date would look like: 8x:17. the 8x would stand for the number of digits in front of the 17 and the :17 are the last digits of the date. This system would be highly versatile as the precision of the date could be specified by the user, for example, a precise, important date could look like this: 0x:3,000,002,017 (or just :3,000,002,017 would work fine) but a quick casual date would look like this: 9x:7.

How the date would be said

For the date 8x:17, the date could be said formally like: "Eight times seventeen", but in casual speak, the date could be said like: "Eight, seventeen" and it would get the point across well enough.


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