calculated column show how many years ago non calendar year

[jasemilly]

Hi I have a datetable, that haddles years that dont run calendat year.  The year start 01/04/2020 for this year and I have a coumn called RailYear.  I would like to create a new calculated column that will show how many years ago that row is 

so for today 26/06/2020 years ago is 0

                    26/06/2019 years ago is 1

at the moment I have hardcoded the caluclated column so railyear - 2020 this works fine.

I have created a table current rail year that hold one value 2020, can I write a dax query that retrieves this value?  I have no realtionship between the tables ?

I am looking to use this value on a clustered graph so the the legend will dynamically change colour so each year ago is a certain colour.

thanks in advance