In the United States (and elsewhere), a Hallmark holiday is 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.
[1][2][3][4] (federal) = federal holidays, (abbreviation) = state/territorial holidays, (religious) = religious holidays, (cultural) = holiday related to a specific racial/ethnic group or sexual minority, (week) = week-long holidays, (month) = month-long holidays, (36) = Title 36 Observances and Ceremonies