Origionally the English billion was 1000000000000. But in the modern world everyone uses the American billion which is 1000000000, like your Milliard. We pobably used the Miliard in the Uk once. Actually I remember reading that word in a book from the 1960's, and thinking it meant million. And it was an English book. It seemed strange. It makes sense now.
It is confusing.
So it is 4 miliard years, 4000000000.
Also another difference between the USA, and hence the UK too, they use commas to denote millions, and points for decimals, while Europe does it the other way around.
______________American and UK_______Europe
Decimal:__________0.1_________________0,1
Million:_________1,000,000___________1.000.000
