Father's Day
Father's Day, is observed on the feast day of Fathers. It is celebrated as a public international day, like in many other countries including the U.S., on the third Sunday of June.
In Greece, like in other European countries, this day is named (Fête des Peres/Feast of Fathers)
Not a Father's Day
Barney is praying to God for help when he receives news that the girl is not actually pregnant. He is so happy he dances down the street to Marshall's office, where he announces he is going to create a holiday for people like him, called 'Not a Father's Day'.