How to translate BC dates into Holocene Era

As you may know, I translate Wikipedia articles into Holocene Era. While doing it for some time now I came up with a bunch of formulas as well as some tips and tricks that may not be obvious to you at first. But if you are going to translate dates from BC to HE, you should know about them.

Precise translation of years

The most common mistake I see people making is thinking that to convert a date from BC to HE you just subtract it from 10 000. To understand why it’s wrong let’s visualize BC dates of previous decamillennium on top of corresponding HE dates:

BC and HE dates form pairs (1 and 10000, 2 and 9999, 3 and 9998, etc), and the sum of each pair is constant and equal to 10 001. So the correct formula for translating a date from BC to HE is: 10 001 – x

For example, Caesar was murdered in 44 BC. In HE that would be (10 001 – 44) 9957.

Imprecise translation of years

Sometimes you can use formula 10 000 – x though. I call it imprecise translation. For example let’s say I’m translating a Wikipedia article and there is a photo of some ancient statue and the caption says that this statue is dated roughly to years 70-40 BC. If I translate these dates using the first formula (precise translation) I’d get 9931-9961. In this case it would be better to use imprecise translation that would give 9930-9960 instead. On one hand, one year difference is insignificant since the statue can’t be dated precisely anyway, and on another hand I get nice round numbers instead of weird numbers ending with 1s (which give an illusion that these dates are precise).

But you should be careful with imprecise translation. First, if a BC year is round it doesn’t necessarily mean that it is not precise. For example Egypt was annexed by Rome in 30 BC. That is a precisely known date even though the year is round, so it should be translated precisely to the year 9971.

Second, there are cases when a date is both round and imprecise, but you still should translate it precisely. For example it is said that Caesar was born circa 100 BC. But it doesn’t mean that since historians didn’t know the precise date, they just picked a nice and round one. Actually, there are a couple of hypotheses of when he might have been born, one suggesting Caesar was born in 102 BC, another suggesting he was born in 100 BC. That means that he was born either in 9899 or 9901. With imprecise translation we’d get year 9900 for his birth, which is the same as year 101 BC and does not agree with any of the two hypotheses.

Third, a lot of the times I translate years precisely just to not cause a mess. For example if some person was born in some year BC that is round and probably not precisely known, and I translate this date imprecisely, effectively shifting it by one year, that may change his age that is mentioned in the article as well. Am I allowed to change person’s age? Also, if I shift his year of birth I’d better be consistent across multiple articles that may mention this person. For these reasons I tend to translate birth-dates precisely even if they are not precisely known.

As a reader of my wiki project (or any text translated into HE) you should keep in mind that if a HE year ends with 1 or 6, it may be a precise translation of a round (and probably not known precisely) year BC ending with 0 or 5.

Translation of millennia and centuries

Everything is much simpler with millennia and centuries. There is only one way to translate them.

For millennia the formula is: 11 – x

For example, 2nd millennium BC is (11 – 2) 9th millennium.

For centuries the formula is 101 – x

For example, 4th century BC is (101 – 4) 97th century.

Translation of decades

With decades it’s a bit more complicated but let’s start with simple stuff first. Let’s look at the 1st century BC or 100th century HE:

The pairs of numbers always give a sum of 9990. So the formula for translating decades is 9990 – x. And it works for any century. For example 320s BC would be translated into 9670s (9990 – 320).

And this is a picture of any century BC:

When you need to translate phrases like ‘20s of 4th century BC’ the short formula that will work for any century is: 90 – x

But you should be aware that decades BC and decades HE don’t match perfectly. Actually they only have an 80% match.

It happens because our decades are shifted by one year. For example a proper third decade of a given century is comprised of years 21 to 30. And a proper eight decade is comprised of years 71 to 80. Proper decade is a term I just invented. If we used decades this way there would be a perfect match between BC and HE decades just like with millennia and centuries.

But instead we call those decades 20s and 70s. 20s are comprised of years 20 to 29, and 70s are comprised of years 70 to 79. So, each decade is shifted by one year relative to corresponding proper decade. And since BC and HE decades are shifted in different directions we have a mismatch of 2 years.

So, you should be careful when translating decades. Especially you should be careful when figuring out whether or not a particular date belongs to a particular decade.

Categorizing dates by decades

This is the most weird stuff. The best way to explain it is to give an example. Let’s say I’m translating a Wikipedia article about some person who was born in year 320 BC. On the bottom of the same article there is a list of categories, and one of those categories is called ‘People born in 320s BC’. I need to translate his birth date as well as the category name.

When I translate his year of birth, it becomes 9681. When I translate the decade 320s BC using the formula 9990 – x, I get 9670s (but the person was born in 9681). The reason this happens is because of the mismatch between BC and HE decades I already told you about. Even if he was born in 321 BC (9680) it would still be in 9680s. See the picture above to visualise it.

So, when you want to categorize a BC date that ends with 0 or 1 by decade you should use formula: 10000 – x, where x is your decade (not date itself). In our example that would be: 10000 – 320 = 9680.

The short formula that would work for every century is 100 – x. This formula would give a weird result for 0s decade, but thankfully I’ve never encountered phrases like ‘in 0s of 4th century BC’.

Automating date conversions

See how easy it is to translate dates with my date conversion tool.


In conclusion let me just list all the formulas.

Precise translation of years: 10 001 – x

Imprecise translation of years: 10 000 – x

Millennia: 11 – x

Centuries: 101 – x

Decades: 9990 -x

Decades, short: 90 – x

Categorization of a date ending with 0 or 1 by decade: 10 000 – x (where x is a decade, not the date)

The same, but short version good for every century: 100 – x

About my BC to HE date conversion tool

You can find this tool here (will open in a separate tab).

You can get an idea of what’s possible with this tool by watching this video:

And this video shows how I translate a typical Wikipedia article:

As you can see, it takes about 5 minutes. There are bigger articles like Alexander the Great of Julius Caesar that can take 30 minutes or more to translate, each. But then there are other, very small ones, where I just need to translate one date, which takes a few seconds.

What you need to know when using my tool

Insert only plain text into it. If you just copy some text from your browser you’ll end up with a mess. Along with year numbers you’ll be highlighting numbers from HTML markup, like RGB color numbers and such.To make rich text plain put it into some plain text editor first. Then copy it from there.

Also, you should know that this tool is pretty dumb and it is not fool-proof. So try to avoid chaotic actions like pressing the same button multiple times in a row.

The window of the editor is made small on purpose. It helps you to focus and not miss anything when you are looking for stuff that needs to be unhighlighted. I made it fullscreen at first, but it didn’t work well for me.

If you don’t understand some of the date conversions, read this small article.

Translating texts for my wiki project vs for other purposes

I created this tool to facilitate translation of Wikipedia articles for my project. You can see in the videos that instead being translated right away dates get wrapped in a special syntax. That syntax is later used by my wiki to finally translate everything.

When you translate texts that are not meant to be published on a wiki website the process is the same, but in the very end you just use the button called ‘Translate finally’ to translate everything inside the editor.

Before final translation you may want to save the marked up version of your text, and use it as a source if you need to fix anything in your text in future.

Why Holocene Calendar is unique

When I discussed Holocene calendar on a couple of history forums people would usually start to suggest other calendars. Or they would start discussing what historical event to choose as a starting point of some new calendar era. It’s as if they think there is a buffet of calendars where they can choose whatever they want. But reality is, if you want to have a calendar that you can use in practice, the choice is very limited.

First, let’s look at history:

Our goal is to have all events in written history marked with positive year numbers. An obvious solution would be to select Event 1 as a start of the new era. But there is a problem. Events in the early history cannot be dated precisely. We can say that Egypt was unified in 3200 BC, but we don’t really know. It’s just an estimate, and it can change in the future. 

So, we can’t use Event 1 as a starting point. At this moment many people would say that there is no solution to this problem, so let’s not bother doing anything about it. But there actually is a simple solution: just put the starting point before written history.

We have to abandon the idea of selecting some historical event as a starting point, because it just won’t work. The starting point has to be before any historical event, preferably with a substantial gap between it and the first historical event. You may say that such a starting point would be arbitrary. First of all, start of Christian Era is arbitrary as well, but it works somehow. And arbitrary doesn’t mean random. We need to select the starting point in such a way that we can easily translate historical literature into the new system. Basically our new system should use the same centuries and millennia as Christian timeline:

I don’t think most people realise how important this is. We should be able to just rename each century and each millennium. If you select the starting point in such way that you can’t just rename millennia, then you can’t easily translate history literature. So you’d have to rely on historians writing new books using your new system, which they will never do. So basically any system that doesn’t utilise the same millennia as Christian timeline is practically useless. 

That leaves us with a very limited number of options. You can use 4000 BC as a starting point, if you want to focus only on written history. In fact I used this system for a number of years before I switched to Holocene Calendar. You may select 3000 BC if you want to be more precise in terms of how long the written history actually is. But in this case you’d have some very first historical events positioned before your new calendar epoch. You can have a bunch of other starting points like 5000 BC, 6000 BC and so on. But I don’t know why you would select them. And finally there is 10000 BC. 

The last option is better than all the rest, because it is easily built into the system that we are used to, the Christian timeline. Even if you use Holocene Calendar as it was originally proposed, it’s very easy to translate dates in Common Era. Just add a 10000 to any date. For example 2021 CE is 12021 HE.

And if you use the modified version of Holocene Calendar where you count years in each decamillennium separately, then you don’t even need to translate dates in the Common Era.

This is very important for translating historical literature, because we have disproportionately more literature related to the current decamillennium than we have literature related to the previous one. If we can just avoid translating CE dates, that’s a huge advantage. 

Look at the amount of Wikipedia articles I’ve already translated into Holocene Calendar era. It would have been impossible if I used some random starting point instead of 10000 BC.

Your comments about Holocene Calendar

You can leave your comments about using Holocene Calendar here. I’m not interested in debating whether it’s a good idea to use this calendar or not. I’ve already done it on history forums. I know that there is no shortage of people who just don’t get it.

I want you to try to use Holocene Calendar and share your experience.

Also, if you have some preferences in terms of what Wikipedia articles you’d like to see translated into Human Era, you can tell me in the comments. I want to translate articles that are in demand before any other articles.