The number of days per year can vary from year to year depending on the number of weekend days. However here’s the standard days per year according to BIR: ftp://ftp.bir.gov.ph/webadmin1/pdf/42126Annexes%20B%20-NPWC.pdf
313 days = Employee working from Mondays to Saturdays
261 days = Employee working from Mondays to Fridays