even when still "in" we kinda celebrated birthdays. that is we hit a bar where they would give a free birthday drink and get drunk. not much has changed, just that we give small gifts (i never know what kind of gifts are "expected", never learned that, hate it). "we" being several other inactive/dfed JWs from the same congregation.
as for christmas, i never learned how to celebrate it, so i pass. i do join public santa claus style festivities though, but i can't see myself putting up a tree and christmas lighting at home.