Show Annual Year

Please see the attached spreadsheet.

I am trying to get excel to workout the annual year based on the cashflow end date.

As you will see, row 6 is currently manually entered. I would like it to increase for each year that increases: so,

2013 = 1
2014 = 2
2015 = 3

Some people mentioned using a MOD function, but I have had no luck?

Any help would, as ever, be greatly appreciated!