Help setting Absence Plan Eligibility

Summary

Howdy, For our business requirements eligibility for any plan is determined based on the date of the holiday.

Content

Specifically, 30 days before the holiday date, and 150 days after the holiday.

For example. If Labor Day falls on 9/6/2020, then employees should only be eligible for the Labor Day absence plan from 8/7/2020 to 2/3/2021.
How can we go about this?