Hallmark Holiday 

A holiday that seems to exist only for the purpose of selling greeting cards (and flowers, etc).

"What the hell, it's Administrative Professionals Day?"
Yep, just another Hallmark Holiday."

Hallmark Holiday by TheMonger May 5, 2006

Hallmark holiday 

Unlike the sanctity of the traditional high holidays, the Hallmark Holiday was invented by the executives of the Hallmark corporation to increase quarterly sales. Generally agreed upon to include Valentine’s Day, Mother’s Day, Father’s Day, and essentially any pseudo- holiday that a card can be sold for.

Jimmy panicked when he realized he hadn’t gotten a card for his dad’s special day, but then quickly relaxed when he realized it was a Hallmark holiday - Father’s Day - and the card was optional.

Hallmark holiday by Grant Rampus June 20, 2021