Is one obligated to follow the official lunar calendar of their country for fasting the White Days, or should they rely on their personal sighting of the moon's fullness?

It is sunnah to fast the Ayyam al-Bid (the 13th, 14th, and 15th of each Hijri month). Their beginning can be determined by sighting the crescent moon, or by completing the previous month as thirty days, or by the lunar calendar adopted in non-Muslim countries. The full moon usually occurs on the night of the fourteenth. There is no objection to relying on the lunar calendar for performing this supererogatory act of worship, because the virtue of fasting three days from every month is achieved by any three days.