Based on what I've seen in this article about relative date ranges it seems as though all relative date ranges for the last n periods of time stop at the time period prior to your current time.
https://help.salesforce.com/articleView?id=filter_dates_relative.htm&type=5
Does anyone know if there is a way to show, for example, last 12 months and have it include the current month's data?
4 answers
Are you just trying to do something like this?
Filtered By:1 OR 2
1. Close Date equals LAST 11 MONTHS
2. Close Date equals THIS MONTH