Part timer accrual formula - consider date track change

Question

Needed some help with part timers accrual formula.
The accrual formula need to prorate the entitlement based on the work hours and accrual bands(years of service).
The accrual formula should account for date track changes to both the years of service and work hours.
How can this be achieved?

Answer 1

This is a common but difficult problem to implement. When I've done this before I've:
1) Used a looping Accrual Fast Formula inside the main Accrual Fast Formula (like the seeded ones), but
2) Built a custom User Defined Fast Formula Function to retrieve the next date of change of hours/years service
3) Called this UDT inside the looping Fast Formula to determine the next change
4) Prorate accruals from the beginning of the year up until the next date of change
5) Loop from the date of change going forward
6) In the next looping iteration call the UDT again to find the next change from now
7) Prorate accruals from now until the next date of change
8) Continue 6-7 until there are no more changes this year.
So in a simple year the looping formula just runs twice: once from the beginning of the year up until the service anniversary and again from the service anniversary to the end of the year. In an example where an employee changes hours it loops three times: once from the beginning of the year up until the hours change (assuming in this case the hours change comes before the service anniversary), then again from the hours change to the service anniversary, and then again from the service anniversary to the end of the year.
In a complex example with multiple hours changes it can loop as many times as needed.