Sheesh, I gave you quite a delay in my answer... I'm very sorry!
In case you still need it, here's one solution that you could try -
I brought in some random 1500 items organized in two tables, as per the screenshot below. The Service Date is a random date between today and 10 years ago.
In PowerBI, you can go to your Table Data and create a new column (be careful not to use "new measure" option):
Last5Y =
var ThisDate = Table1[Last Known Service Date]
var FiveYearsAgo = DATE(YEAR(TODAY())-5,MONTH(TODAY()),DAY(TODAY()))
return
ThisDate >= FiveYearsAgo
Now that we have a new column, we can create a measure ("new measure" option) that will check the % of "True" flags for a selected region:
Last5Y% =
COUNTROWS(
FILTER(
Table1,
Table1[Last5Y] = True)
)
/
COUNTROWS(
Table1
)
Here's an example for EU:
It matches what I have calculated in Excel: