Mother's Day was an event on Lissepia. Mother's Day featured planet-wide celebrations.
On Lissepian Mother's Day in 2365, the planet's Central Bank was robbed in an incident that became known as the Lissepian Mother's Day Heist. (DS9: "Who Mourns for Morn?")
This festival may be similar to the current-day Human Mother's Day tradition, though it was not explicitly said to be anything else then an one-off event.