Vacation and Sick leave
The Labor Code treats vacation leave and sick leave under the same category as Service Incentive Leave or leave with pay.
Thus, the grant of vacation or sick leave with pay of at least five days may be credited as compliance with SIL. For example, if a company is giving its employees 15 days vacation leave, five days of which is with pay, the five-days paid vacation leave may be credited as SIL.
Employees entitled to SIL
Every employee (subject to the exceptions below) who has rendered at least one year of service is entitled to yearly service incentive leave of five days with pay.
“At least one year of service” Meaning
The term “at least one-year service” means service for not less than 12 months, whether continuous or broken.
The 12-month period shall be reckoned from the date the employee started working, including authorized absences and paid regular holidays.
However, where the operation of the establishment as a matter of practice or policy, or that provided in the employment contract, is less than 12 months, such period shall be considered as one year.
http://www.laborlaw.usc-law.org/2010/02/27/service-incentive-leave/