Civil Code of the Philippines (Art 13)
When the laws speak of years, months or nights, it shall be understood that years are of three hundred sixty-five days each; months, of thirdy days; days, of twenty-four hours; and nights, from sunset to sunrise.
If months are designated by their name, they shall be computed by the number of days which they respectively have.
FIRST DAY EXCLUDED, LAST DAY INCLUDED
In computing a period, the first day shall be excluded and the last day included.