I saw this on DriveThru RPG DTRPG); https://www.drivethrurpg.com/featured.php?promotion_id=GMD19_bundles some of the sales only run for GM’s Day, but others run for a week. Additional GM’s Day sales: https://www.drivethrurpg.com/rpg_gmsday.php.
GM’s Day, March 4, 2019: https://www.checkiday.com/45fdd4a65d032ddf6eba5adc51fccbfc/international-gms-day.
Facebook page: https://www.facebook.com/GMSDAY/
Today we celebrate game masters, who are known as GMs for short. Spunkrat, a user on EN World‘s message board who later changed their username to Heathen72, made a post on December 4, 2002, proposing the idea for a day honoring GMs. They asked for suggestions for a date, and a user named Mark suggested March 4, because it was not only a date but a command that may be used in a role-playing game—”march forth.” This is the date the messageboard community settled on, and the day spread to the rest of the role-playing game community. On today’s holiday, the work GMs do is celebrated, and they are given thanks and gifts. Deals on role-playing games can often be found in stores and from game publishing companies. Since 2008, the day has held greater significance, because Dungeons & Dragons co-creator Gary Gygax* died on the holiday that year.
*Gary Gygax’s memorial on Find-A-Grave: https://www.findagrave.com/memorial/25074706/gary-gygax – no cemetery listed as the memorial indicates Cremated, location of ashes unknown. Which doesn’t make sense as there is a headstone photograph on the memorial.