Valentine's Day (real world)
From Jenny Everywhere Wiki
Multiple Jenny Everywhere-related works have been released on the occasion of Valentine's Day. The day is of further significance as the date of the original debut of the Crew of the Copper-Colored Cupids, meaning multiple anniversary stories in the series were also released on that date.
Also notably, the first completed Jenny Everywhere comic story, COMIC: 'My Bloody Valentine, took place on Valentine's Day (as the title indicated), though whether it was released on the day itself is lost to history.