Best approach to calculate AnnualLeave proration change of Parttimers to Fulltimers, FT-PT and PT-PT

Summary:

We have a requirement to calculate the Annual Leave proration for

a) Full-timer to Part-timer,

b) Part-timer to Full-timer and

c) Part-timer to Part-timer

Example:

FT-PT (35 Hrs to 28.8 Hrs) FTE - 0.8

PT-FT (28.8 Hrs to 35 Hrs) FTE - 1

PT-PT (28.8 Hrs to 22.6 Hrs) FTE - 0.6

The changes from FT-PT, PT-FT, PT-PT for the users can happen multiple times in a calendar year (Jan1st to Dec31st).

Example:

Jan - March User is a Full timer 1FTE (Absence calculations to be applied)

April - June User is a Part-timer 0.8FTE (Absence calculations to be applied)

July - August User changes from Part-time 0.8 fte to Part-time 0.6 fte (Absence calculations to be applied)