How can we convert between a.t.b. and Revolution Year?


In the first two seasons of _Code Geass_ , dates are mentioned with "a.t.b.".
I took this screenshot from first episode of season one:

!["2010 a.t.b., August 10th"](https://i.stack.imgur.com/wZjkw.jpg)

However, in _Code Geass: Akito the Exiled_ , dates are mentioned as R.Y.
(Revolution Year). This is a screenshot from the _Akito the Exiled_ trailer:

!["Revolution Year 228; EU - Europe United
Alliance"](https://i.stack.imgur.com/fgvX0.jpg)

So, first question: **What does a.t.b. stand for?**  
And, also: **How can we convert between a.t.b. and R.Y.? Which Revolution Year
would 2010 a.t.b. be?**




> **What does a.t.b. stand for?**

It stands for "Ascension Throne Britannia", named after the "date the first
Celtic super-king, Eowyn, was elected by the united British tribes to battle
Rome, becoming the first member of the modern Britannian imperial
family."[{1}](http://codegeass.wikia.com/wiki/World_History) 55
[B.C.](http://en.wikipedia.org/wiki/Anno_Domini) is equivalent to 1 a.t.b.

* * *

> **How can we convert between a.t.b. and R.Y.?**

The Revolution Year system (used by the EU in _Code Geass_ ) is based on the
French Revolution (start date) of 1789
A.D.[{2}](http://en.wikipedia.org/wiki/French_Revolution)[{3}](http://codegeass.wikia.com/wiki/European_Union#Akito_Worldview_Columns)
Since 55 B.C. is 1 a.t.b., we can figure out the actual conversion formula:

> 0 R.Y. = 1789 A.D. = 1845 a.t.b.

If you want a simple conversion between a.t.b. and R.Y., just some simple
math:

> R.Y. = a.t.b. - 1845

* * *

> **Which Revolution Year would 2010 a.t.b. be?**

Based on the conversion above, a.t.b. 2010 is equivalent to R.Y 165.




> **What does a.t.b. stand for?**

It stands for "Ascension Throne Britannia", named after the "date the first
Celtic super-king, Eowyn, was elected by the united British tribes to battle
Rome, becoming the first member of the modern Britannian imperial
family."[{1}](http://codegeass.wikia.com/wiki/World_History) 55
[B.C.](http://en.wikipedia.org/wiki/Anno_Domini) is equivalent to 1 a.t.b.

* * *

> **How can we convert between a.t.b. and R.Y.?**

The Revolution Year system (used by the EU in _Code Geass_ ) is based on the
French Revolution (start date) of 1789
A.D.[{2}](http://en.wikipedia.org/wiki/French_Revolution)[{3}](http://codegeass.wikia.com/wiki/European_Union#Akito_Worldview_Columns)
Since 55 B.C. is 1 a.t.b., we can figure out the actual conversion formula:

> 0 R.Y. = 1789 A.D. = 1845 a.t.b.

If you want a simple conversion between a.t.b. and R.Y., just some simple
math:

> R.Y. = a.t.b. - 1845

* * *

> **Which Revolution Year would 2010 a.t.b. be?**

Based on the conversion above, a.t.b. 2010 is equivalent to R.Y 165.

