Except there was never a "Year 0."
The Gregorian calendar was created by 6th Century monk called Dionysius Exiguus, AKA "Denis the Short," who used Biblical references to fix the date of the birth of Jesus and created his new calendar, which was first implemented by Pope Gregory XIII in 1582, hence the name "Gregorian calendar."
Except Dennis the Short died in 544 AD, a good six or seven centuries before the full Arabic numeral system (which was actually Indian in its origin) reached Europe. Before that, there was no numeral zero (or other representation of a null number) in Europe. So Dennis couldn't have had the Gregorian calendar (which we still use today) start in the year 0, even if he'd wanted to, because he didn't have the zero.
And if the first year was the year one, then it necessarily would have to follow that the one-hundredth year was the year 100. So the first year of the 2nd Century AD was the 101 AD. Not 100, 101.
Which also necessarily means that all of you who celebrated the turn of the new Century on New Years Eve of 1999 were 366 days early. The 21st Century actually began on January 1, 2001.
Because there was NO YEAR 0.
And Dennis also got the Year 1 wrong because archaeology since has proved that Herod was dead by no later than 4 BC.
Or, did you intentionally miss my point just to show us how smart you are?