[coldtea]

Doesn't matter, we can just agree the first century had 99 years, and be done with it.

We have special rules for leap years, that would just be a single leap-back century.

At the scale of centuries, starting 2nd century at 100 as opposed to 101 is just an 1% error, so we can live with it. For the kind of uses we use centuries for (not to do math, but to talk roughly about historical eras) it's inconsequential anyway.