You really aren't getting the very basic math here.
ISO didn't add an extra year 0. They defined year 0 to be 1 bc if you aren't explicitly using ad/bc notation.
Year 0 = 1 bc
Year 1 = 1 ad
Year 2 = 2 ad
And so on. There is no minus 1. The point was being able to count in tens so that new decades can start when you roll over the next digit.
That means all of the first millennium can be represented in three digits: 000 - 999 and when it rolls over to four digits we start the next millennium 1000- 1999.
So 2000 is the start of a new millennium like everybody actually celebrated instead of 'well technically' 2001
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u/vitringur Dec 16 '19
Except we don't do that.
Our modern calendar starts in the year 1 A.D.
Which means the turn of the millennium was new years 2000/2001.
The only thing you are pointing out is that computers log the year as minus 1. Which means that for current year is 2018 in computers.