See - sc.judiciary.gov.ph/jurisprudence/2013/june2013/157020.pdf
"x x x.
A.M. 00-2-14-SC clarifies the application of Section 1, Rule 22 of the Rules of Court when the last day on which a pleading is due falls on a Saturday, Sunday, or legal holiday and the original period is extended.2
The clarification states:
Whereas, the aforecited provision applies in the matter of filing of
pleadings in courts when the due date falls on a Saturday, Sunday, or legal
holiday, in which case, the filing of the said pleading on the next working
day is deemed on time;
Whereas, the question has been raised if the period is extended ipso jure to the next working day immediately following where the last day of the period is a Saturday, Sunday or legal holiday so that when a motion for extension of time is filed, the period of extension is to be reckoned from the next working day and not from the original expiration of the period;
NOW THEREFORE, the Court Resolves, for the guidance of the Bench and the Bar, to declare that Section 1, Rule 22 speaks only of “the last day of the period” so that when a party seeks an extension and the same is granted, the due date ceases to be the last day and hence, the provision no longer applies. Any extension of time to file the required pleading should therefore be counted from the expiration of the period regardless of the fact that said due date is a Saturday, Sunday or legal holiday. (Emphasis supplied)
x x x."
