Technically, JOL Day actually started earlier this year as a "test" of sorts, but I think the general consensus among the Halloween folks here was that it was going to be a "new" addition to the MMC Holidays (Rudolph Day, Tom Turkey Day).
I don't believe that you had signed up yet here by the time we did our last JOL Day of 20', which would have been on August 31st. I had the first ever JOL Day in March of 2020, after being amazed with SyFy's Friday the 13th Marathon, specifically how much that evening "felt" like an October evening. I liked the feeling so much I had my first JOL Day by myself two weeks later, on the 31st of March. A few more folks have decided to celebrate it, and it is our hope that it grows in popularity for 21'.
We even have a thread for celebrating Jack O Lantern Day :
https://mymerrychristmas.com/forum/threads/celebrating-jack-o-lantern-day.221619/
But yeah, that's where my head is right now, already thinking forward to January, and knowing that we get a sampling of what you would call the "Christmas Triumvirate", which is Rudolph Day on the 25th, Tom Turkey Day on the 28th, and then closing out the longest month of the year with JOL Day on the 31st! I've got everything planned now for JOL Day #1, so look for me to spill the details here over the next week
EDIT:: I just checked the thread, and yes, you were here in time for the Last JOL Day of 2020! So that's awesome! I think this was right around when you joined here