The idea of a special day to honor fathers and celebrate fatherhood was
introduced from the United States. A woman called Sonora Smart Dodd was inspired by the American Mother's Day celebrations and planned a day to honor fathers early in the 20th century. The first Father's Day was celebrated in Spokane, Washington on June 19, 1910.
My problem with Father's Day is not the crass commercialisation of an important relationship, but rather the vexed question of where the apostrophe (if any) goes!
Option 1. Fathers Day: no apostrophe
The argument here is that fathers do not own the day, so no possession is involved and no apostrophe is needed. We are describing a day for fathers, not a day belonging to fathers.
Option 2. Father's Day: an apostrophe before the s
Here the argument is that the day belongs to one specific father (yours presumably). So, because possession is involved, Father's Day needs an apostrophe.
Option 3. Fathers' Day: an apostrophe after the s
Here the argument is that the day is shared among all fathers collectively. Thus the need for an apostrophe after the s.
For now, I'm sticking with choice 1, but I reserve the right to move to option 2 if I feel like it. The only thing I'm sure of is that the names of holidays are written with an initial capital, so it's definitely Fathers Day, not fathers day, regardless of where you put the apostrophe.