So it depends on what you want to use , the Index for if this will work...but one way is to find the last date of sales and create a "MAX Date" as a dimension
[Max Month of Sales]
we can then use this to create an index, based on this date
DATEDIFF('month',[Date],[Max Month of Sales])*-1
Hope that helps, but let me know if it's not going to help in what you want to do with this index
Indexing from Event.twbx 45.6 KB
It works and many thanks!