Absence: Framework for a leave carryover across multiple years with balance for each year

We are working on vacation carryover for Ethiopia. Ethiopian law says employees must be able to carryover any unused vacation days for up to two years. Example: an employee could carryover 10 days from Year 1 into Year 2, use 8 of those 10 carryover days in Year 2, and carryover the remaining 2 days into Year 3. At the end of Year 3, any remaining days from the first year would be forfeited.

To further complicate things, the carryover process is derived off the individual's anniversary and not a common calendar year date. We have adjusted accumulator periods to be based on anniversary month. We process monthly payroll so the carryover process will trigger when the individual's anniversary month = the month being processed.