For each time off type, you can specify if accruals are prorated at the beginning and end of the policy, or are never prorated. If accruals are NOT prorated: The full accrual amount will be added to the user's time off balance on each accrual date.
  • If accruals are prorated: On the policy's first accrual date, and on the policy's end date, the amount the user accrues is proportional to the amount of time the user worked in the preceding "accrual period" (the length of time between scheduled accruals).
  • A policy's end date occurs either when a new policy becomes effective, or the employee's employment end date is reached.
  • The time off earned between the last accrual and the policy's end date is accrued on the policy's end date, even if it is not a scheduled accrual date.
At the beginning of the policy, the amount accrued is:
(amount of time from the policy's effective date to the first scheduled accrual date (divided by) / amount of time between scheduled accruals) X the full accrual amount
 
At the end of the policy, the amount accrued is:
(amount of time from the policy's final scheduled accrual date to its end date (divided by) / amount of time between scheduled accruals) x the full accrual amount
 
For example:
Tim starts his new job on October 1, 2008. He is assigned a Vacation time off type that accrues 12 days on January 1st of each year. On January 1, 2009:
 
If accruals do not prorate for his Vacation policy, he will accrue 12 vacation days off. If accruals prorate for his Vacation policy, he will accrue 3 vacation days off, calculated as follows:
= (amount of time from the policy's effective date to the first scheduled accrual date (divided by) / amount of time between scheduled accruals) x the full accrual amount
= ((3 months (October 1 to January 1)) / 12 months) x 12 days
= (1/4) x 12 days
= 3 days

Please refer the images below which show examples of how prorating occurs at the beginning and end of a policy that accrues monthly.