"When in Rome.."

That's pretty good advice, and you'll probably find that BP is used primarily in dates that are long, long ago. I've seen BC dates given without bothering to include the BC in writings about, e.g., the classical Greeks. I find it a little disconcerting after doing the math to discover that Euclid was roughly minus 60 years old when he died. Sometimes I wish that historians would (speaking of "When in Rome...") use dates measured from the founding of the city.