How can we convert between a.t.b. and Revolution Year?
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} 55 B.C. 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}{3} 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.