Sneaky Paladin said:
I always thought it worked like birthdays and you aren't 1 year old when your born but you are when you have lived for 1 year
... That has nothing to do with... Anything?
Yeah, you're 1 year old a year after you are born.
That's common sense.
However, if you are going to count from year 1 (being the first year), including it, the 100th number is... Well... 100.
So, if you use this logic, the first century began on 1/1/1 and ended on 31/12/100.
Also, by this logic, assuming a single year cannot have a century beginning AND ending in the same year (eg: first century ended on 31/12/100 which implies the second can't have begun on 1/1/100), one must infer that the second decade started on, oh look, 1/1/101.
So unless you are going to have a "century" with 99 years, which is, obviously, a huge contradiction, we must assume that it's 1-100, 101-200, 201-300, 301-400, 401-500, 501-600, etc.
This logic can also be applied to decades also, 1-10, 11-20, 21-30, 31-40, etc.
Therefore, decades/centuries/millennia can be said to BEGIN in years ending with 1, and END in years ending in 0.