Annual Leave on prorata calculation for new joining in between the calendar year

Hello All,
We have leave policy is as follows, also note we credit leaves at the starting of every year
PL: 28
SL: 7
* Out of 28 PL only 18 will be carry forwarded next year.
*Maximum accumulation of PL is 50 and SL is 28.
Please help me with excel formula for prorate leave entitlement formula for employees who join in middle of the year

Hi,
This formula will be based on year calculation.
Type of leave & Qty - PL-28
Number of month in year - 12
Starting of leave calculation(suppose)- April
Joining month (suppose)- November
So calculation- 28/12*(Nov. to Mar.balance months)
28/12*(6)
12 leave can provide
Pls calculate average date for joining in middle of month.