Just an excerpt from your wonderful post, but since when does colloquial reference become mathematical fact?
It's 90s, not 90's... sorry for being anal about the use of the English language but it kind of goes with the academic territory that you have ventured into.
I totally agree that 10 years can happen over any period, you are spot on there and that's not what I'm arguing. But let's not get that mixed up with the sequential order of the calendar, which is the accepted measure.
You are actually agreeing with me with your baby born analogy when you say, "a baby isn’t automatically 1 when it is born..."
The St George NSWRL first grade team were born in the season of 1921.
1921 was season No. 1
1922 was season No. 2
1923 was season No. 3
1924 was season No. 4
1925 was season No. 5
1926 was season No. 6
1927 was season No. 7
1928 was season No. 8
1929 was season No. 9
and 'lo and behold...
1930 was season No. 10
Our first season in the Big League actually works in well with the year dot. If our first season was in 1 AD, our first decade would conclude at the end of season 10 AD.
Yes... it is footy related.