Herodotus mentions that Persians celebrated their birthdays, as if reporting on an odd custom.
In Puritan Massachusetts Bay Colony in the 17th century, it was against the law to celebrate Christmas because it was considered a Catholic invention. You were expected to work on Christmas Day unless it fell on a Sunday.
The actual dates of these events may have vanished into antiquity, but one of the things to keep in mind about the Gospels is that their message is supposed to transcend time.