A period fixed by hours shall commence immediately.
Where a period is fixed by days, weeks, months or years, the first day does not count for the purpose of calculation, unless it is prescribed by law that the period shall commence as of the immediate day.
If a period does not run from the beginning day of a week, month or year, it ends with the expiration of the day preceding the day of the last week, month or year which corresponds to that on which it began to run; provided that, if a period is fixed by months or years and there is no corresponding day in the last month, the period ends with the expiration of the last day of the last month.
If the last day of a period falls on Sunday, national holiday or any other holiday, the day following that day shall take its place, and if the last day of a period falls on Saturday, its last day shall be the Monday morning of the following week.
If a period has to do with any punishment to be imposed upon or any adverse administrative disposition to be rendered against a person, the beginning day shall be the whole day thereof regardless of any hour of the day; and if the last day falls on Sunday, national holiday or any other holiday, it shall ends on that day, unless it is more advantageous to the person if calculated in the manner set forth in paragraphs 2 and 3 hereof.

Where an application based on law or regulation is submitted to an administrative authority by registered mail, it shall be deemed to have been duly filed on the day it is posted as shown by the postmark

Where an application based on law or regulation can not be filed within the statutory period by reason of an act of God or any event not attributable to the applicant, the applicant may apply for restoration to the status quo ante within ten days after the cause [preventing the filing] vanishes. If the statutory period is less than ten days, an application for restoration to the status quo ante may be made within the corresponding number of days.
When applying for restoration to the status quo ante, the administrative procedural act that should have been done within the statutory period shall be carried out at the same time.
No application for restoration to the status quo ante may be made upon the lapse of the statutory period for one year or more.

Unless otherwise provided by law, an administrative authority shall establish and announce by a public notice the time periods required for processing various categories of applications filed by the people under law and regulations.
In the absence of processing time period established and announced under the preceding paragraph, the processing time period shall be two months.
Where an administrative authority is unable to complete the process within the time period established in pursuance of the two preceding paragraphs, the process may be extended to the extent of the original processing time period, but for once only.
In the circumstance referred to in the preceding paragraph, the applicant shall be notified of such extension prior to the expiration of the original processing time period.
Where an administrative authority is prevented from processing its business by an act of God or any other event not attributable to it, the processing time period shall stop running until the discontinuation of such event.