B.C. and A.D.
In the modern calendar, we label all years with B.C. (before Christ) or A.D. (anno domini, or "in the year of our lord"). There is no "zero" year -- the year Christ was born is 1 A.D., and the year preceding it is 1 B.C.
This practice was first suggested in the sixth century A.D., and was adopted by the pope of that time. It took quite a while for it to become a worldwide standard, however. Russia and Turkey, for example, did not convert to the modern calendar and year scheme until the 20th century.
One interesting side note: Because of a variety of changes and adjustments made to the calendar during the middle ages, it turns out that Jesus was most likely born in what we now think of as 6 B.C., and likely lived until 30 A.D..
For more information on time and related topics, check out the links on the next page.