Section 4
SEC. 4. The approximate dates of the above enumerated Muslim holidays may be determined in accordance with the Muslim Lunar Calendar or appearance of the moon or upon Islamic astronomical calculations, whichever is possible or convenient: Provided, That the President shall be advised of the approximate dates of the above Muslim holidays at the start of the calendar year but not later than the 15th of January by the Muslim community and/or by the Islamic Directorate of the Philippines, Inc. in order that appropriate publication and announcement could be made to correspond with the Gregorian-calendar.