Due to years of concerts, moves, distance, etc, my family rarely celebrates Mother's Day on the correct day. It's frequently combined with Father's Day for a Parent's Day. For these holidays, gifts are given to my mom, dad, and grandmother.
In DH's family, it's required to buy Mother's Day gifts for all mothers in the family, not just your own mother or grandmother. The same goes for Father's Day. This means that each year I'm expected to buy 7 Mother's Day gifts and 4 Father's Day gifts each year (DH has a lot of siblings, etc.).
What odd family traditions does your family have over the holidays?