Sick Balances per sick year

Hello,

We face a weird requirement about sick balances and any idea on that would really be very helpful.

The requirement is as following:

The employees are granted with their sick available balances of i.e 30 days from their First day of employment.

Let's suppose that an employee is hired on 01/01/16. On 15/04/16 he takes 5 days of sick leave and after that he takes 3 additional days of sick leave on 30/07/16. Then the available sick balance is 22 days. These 22 days will be available till the anniversary of the First sick event date. That means that no rollover will happen neither calendar nor fiscal nor anniversary on Hired date etc but the employee will have this balance till the 15/04/17 which is the anniverary date of the First sick event. Reaching that date of 15/04/17, the employee will have