eazyBI does not have default support for Time hierarchies with such long periods. You can define custom Time hierarchies using 2,3,4 week periods, though.
You can consider defining a new custom Time hierarchy with 3 week period to represent Sprint cycles. Then you can define PI members as calculated members using those new Sprint cycles.
Define a new custom time hierarchy with 3 weeks and 2020-10-12 as a start date to get correct cycles:
Select this 3 week level in the report and bookmark periods for a particular PI:
Define a calculated member with the function Aggregate and select all bookmarked sprint cycles to the formula within a formula:
You can define PI cycles with default Weekly hierarchy members as well. However, it might pull in 3 times more weeks and can slow down a report a bit.
You can repeat the same for other PI periods. Then you can use those calculated members in the report.
Daina / firstname.lastname@example.org