Mother's Day is a day of thanks given to female parents by their children on Lissepia, much like the ancient Earth holiday known by the same name. Mother's Day on Lissepia is known for its' festivities and seemingly widespread celebrations.
On Lissepian Mother's Day in 2365 the planets' Central Bank was robbed in an incident that became known as the Lissepian Mother's Day Heist. (DS9: "Who Mourns for Morn?")