Upfront Absence quota for the new Hire

I have a Time Quota scenario for a country. I would need your advise/solution.

Quota: Annual Leave

Entitlement: 23

1. For the new Hires, quota should transferred on the Hire date (Prorated by Days) for Example: employee joins on 2^nd January then (23*364/365), Then rounded up to nearest .5 or 1.
2. Subsequently every 1^st Jan, new entitlement should be generated. Start and End date of quota is 01.01.2014 to 31.12.2014

My understanding/Solution

1. Use a time type in the Base entitlements.
2. Maintain Yearly entitlement value in T511k
3. Use a Date type for Hire in IT0041 to query in PCR for the Hire date. Etc. Etc.

I am stuck on the Proration of Quota for new hires. How do I count days between Hire date and End of Year.?

Regards

SNC