The first year of our calendar was "0." The calendar isn't based on some theoretical "day 1." the calendar is based on how long it's been since the birth of Christ. (I realize historians think it's off but that's the theory). So the year 1, was one year after the birth and Jan. 1 will be 2,000 years since the birth. Probably shouldn't have opened this can of worms, but what the heck, it's a slow day.