After Accrual Plan changes, Leaves Getting accrued as per new plan in older dates??

Dear All,

One of my client having 2 different PTO Plans, Accrual Plan 25 & Accrual Plan 36, when employee promoted from one plan to another, it's calculating the accruals properly but when you jump to any older dates, it's accruing as per the new plan where this new plan is not there on the given date.

Example: Employee having Accrual Plan 25 (Approx 2 days per month), as he/she got promoted, plan got end dated on 31-mar-2018, New Accrual Plan 36 is attached to the same employee on 01-Apr-18, so employee new plan started and accruing the leaves properly but if i go to any older date before 01-Apr-18, it is accruing as per the new plan i,e, 3 days per month.