Hallmark Holiday

"Hallmark Holiday" is a term used predominantly in the United States to describe a holiday that is perceived to exist primarily for commercial purposes, rather than to commemorate a traditionally or historically significant event. The name comes from Hallmark Cards, a privately owned American company, that benefits from such manufactured events through sales of greeting cards and other items. Holidays that have been referred to as "Hallmark holidays" include Grandparents Day, Sweetest Day, Boss's Day, and Administrative Professionals' Day / Secretary's Day. Some people also consider St. Valentine's Day, Mother's Day and Father's Day to be widely abused by marketers, turning them into such days.

In most cases, the card maker didn't invent the day outright - they just took something which was marginal, limited to a regional scope or intended for some other (non-commercial) purpose and misused it in a disproportionate manner as a marketing opportunity. Yes, there are many other culprits, ranging from florists to confectioners to rival greeting card makers, but the Hallmark company became the Trope Namer because of its relatively high profile.

Advertising

 * The Hallmark corporation maintains that it "can't take credit for creating holidays."
 * Circle K Mexico was forced to apologise for a 2019 'Secretary Day' ad promoting a deal on chocolate, red wine and condoms. In the #MeToo era, commercialisation is one thing, but sexualisation is a no-no.

Anime and Manga

 * In Lucky Star, Kagami goes out of her way to specifically not complain that Valentine's Day was created by the chocolate and card companies.

Tabletop Games

 * In the In Nomine adventure "A Very Nybbas Christmas" (available as a free download from Steve Jackson Games), the infernal horde attempt to use the "Christmas in July" Hallmark Holiday to undermine Christmas as a sacred event and promote selfishness above selflessness (tipping the balance on Earth toward Hell) at the same time.

Western Animation

 * In The Simpsons Season 9 episode "Trash of the Titans", Costington's Department store creates a new August holiday called "Love Day." As Lisa puts it, this is intended to boost sales.  Costington's sales chart (as shown in the episode) depict a dip from July to September.

Real Life

 * Mother's Day (US version, established 1908 as the second Monday in May) was created by Anna Maria Jarvis as a memorial to her own late mum (deceased in 1905). The confection, floral and greeting card industries moved quickly to commercialise various aspects, particularly the white carnations which she had adopted as a symbol. After years of fighting their efforts in vain, including a trademark battle, she died penniless in an insane asylum.
 * National Grandparents Day (US version, proclaimed 1978 by President Carter as the first Sunday after Labour Day) was intended to educate youth about important contributions made by seniors throughout history and urge youth to "adopt" a grandparent, not just for one day a year, but for a lifetime. The intention was never commercial.
 * Secretaries Day (Wednesday of the last full week of April) was contrived during a World War II labour shortage by National Secretaries Association president Mary Barrett, Dictaphone Corp. president C. King Woodbridge and Young & Rubicam ad agency execs Harry F. Klemfuss and Daren Ball. It was renamed "Administrative Professionals Day" by its parent organisation, which is now called the "International Association of Administrative Professionals". Other countries have their own Secretaries/Administrative Professionals Day that fall in different dates: while April or May are the most common months for it, in Latin America it tends to be celebrated on the last day of September.
 * Singles' Day (11/11) is heavily commercialized in communist mainland China. It is not commemorated elsewhere, as it conflicts with Armistice Day (1918-11-11), which ended the Great War and became the day of various war memorials.
 * November 11th has also become Pretz & Pocky day in Japan and Peppero Day in Korea, with said companies encouraging the gifting of their products on said date in a low rent "Valentine Day" rehash.
 * Sweetest Day (Third Saturday in October) was invented in 1921 by Cleveland newspaper The Plain Dealer and is notable only regionally in the US Midwest.
 * White Day, in Japan, China, and some other east-Asian countries. According to The Other Wiki, it "was started by the National Confectionery Industry Association as an "answer day" to Valentine's Day" in 1978.
 * "Black Friday" originated in Philadelphia in 1961, where the term was used to describe the traffic disruptions that took place the day after US Thanksgiving. It took only four decades for the term to be co-opted to refer to the busiest shopping day of the year.
 * Super Bowl Sunday, or "Big Game Sunday" if you aren't willing to pay the license fee to use the term "Super Bowl", has become the second-largest food consumption event in the United States (after Thanksgiving) and the day when all the "important" commercials are premiered. The US Bureau of Labor Statistics says 4% of the US workforce already take at least part of the following Monday off work.
 * Friendship Day. First created during The Roaring Twenties by the greeting card industry and originally proposed to be on August 2nd, the interest was revived in 1958 when a Paraguayan tried to promote an "International Day of Friendship" to be celebrated on July 20th, a date that became popular in Argentina, Brazil and Uruguay as a day to greet friends and hang out together - most restaurants are completely booked for that day, and mobile networks collapse for the amount of well-wishing messages not unlike Christmas or New Year day . Other countries had adopted different "Friendship Day" dates: in Mexico and Peru is July 14th; in Bangladesh, India, Malaysia and the United Arab Emirates is celebrated on the first Sunday of August, and in some other countries is conflated with Valentine's Day.