I think something only becomes a "tradition" when those celebrating it are too young to remember when and why it started and carry on celebrating whatever it is "because it is traditional". Mother's Day for instance is a fairly recent celebration in Britain, only dating back to the 1940's. Father's Day is an even more recent import dating back to the 1970's in Britain, probably encouraged by the card-making industry. I am sure there are many other similar examples of recently acquired "tradition".