You can use shorthand and say "November 2001." Or you can say the day that HP's 3000 music died. November 14 still marks the start of the post-HP era for MPE/iX as well as the 3000 hardware HP sold. It took another two years to stop selling the PA-RISC servers the company had just revamped with new models months before the exit-the-market announcement. PCI-based N-Class and A-Class, the market hardly knew ye before you were branded as legacy technology.
For a few years I stopped telling this story on the anniversary, but 12 years ago I cut a podcast about the history of this enterprise misstep. (Listen by clicking the graphic above) HP lost its faith in 2001 but the customers hadn't lost theirs and the system did not lose its life. Not after November 14 and even not today. Not a single server has been manufactured since late 2003, and even that lack of new iron hasn't killed MPE/iX. The Stromasys emulator Charon will keep the OS running in production even beyond the January 2028 date MPE/iX is supposed to stop keeping accurate dates.
Red Letter Days were so coined because they appeared on church calendars in red. They marked the dates set aside for saints. In 1549 the first Book of Common Prayer included a calendar with holy days marked in red ink; for example, Annunciation (Lady Day), 25th March. These were high holy days and holidays. The HP 3000 came into HP's product line on a November in 1972. November is a Happening read the banners in the HP Data Systems Division. No day of that month was specified, but you might imagine it was November 14, 1972. That was a Tuesday, while the 2001 date fell on a Wednesday. A total of 1,508 weeks of HP interest.
Something important happened in that other November of 29 years later. Hewlett-Packard sent its customers into independent mode. Those who remained faithful have had a day to mark each year, logging the number of years they've created their own future. It's 17 and counting as of today.