Exactly right. A feast day is to commemorate an event, even if we donât know for sure the exact day it happened, and it is often set to coincide with another event. Thus, we donât know the date of Christâs Transfiguration before the apostles, but we celebrate the Feast of the Nativity on August 6th, because that was the date in 1456 when news reached Rome that the Ottoman invaders had been repulsed at the Siege of Belgrade. So, Pope Callixtus III chose that date to celebrate the Feast Day of the Transfiguration, as an honor to the defenders of Belgrade.
Technically, itâs âThe Feast of the Nativityâ on the liturgical calendar, not Christmas.
Birthdays held no special significance in the middle east at the time Jesus was born, especially to the common folk (they didnât celebrate birthday parties, Jews didnât trust horoscopes, and you didnât have an ID card it went on), so it wasnât considered important. Thatâs true now in many cultures, too - many people from the middle east who were born in poverty donât know their DOB, and will either use January 1 or just make one up when they come to the U.S.
If we donât know the true birth date of an adopted child, we usually pick a date or use the date they are adopted or some date with special significance. Just because we donât know the DOB of the child, thatâs no reason not to celebrate it.
Iâve never understood why atheists, pagans, and some fundamentalists think this is an important issue.