For the calculation I'm trying to perform one year = one season and the data I have is start year and end year.
So 1952 1953 needs to add up to 2 (seasons) but if I use =YEAR(A1)-YEAR(A2) the result is 0 - is there a simple way to include the start year and end year as a value in these calculations?
It looks like you have found the problem and rectified it. For the benefit of others who might have found this thread, this is why it was behaving the ways it was.
Background - Excel (and many other applications) treat dates as 1 for every day past Dec 31, 1899. Today happens to be 42,079. Time is a decimal portion of a day so 42,079.75 would be Mar 16, 2015 06:00 PM.
You had the years as numbers in A1:A2; not as full dates. Using the 1-per-day formula, 1952 is May 5, 1905 and 1953 is May 6, 1905. If you peel out the year of each of those with the YEAR() function, you are subtracting 1905 from 1905; resulting in zero.
The solution would be to either type full dates into A1:A2 and format the cells as yyyy so they display 1952 & 1953 but retain their full date nature e.g. =ABS(YEAR(A1) - YEAR(A2)) + 1 , or use the years as numbers only and discard the YEAR() function altogether, e.g. =ABS(A1 - A2) + 1 to get the spanned (inclusive) number of seasons.
