When does this usually happen? Or did or does it only happen once?

I don't know but it might have been re-named Fireside, there's a subetapedia article for that. If it was a one time event I'm sure an older user might drop by and let you know. ^_^ Happy Morostide!

It appears to be seasonal, although we've only celebrated it the once and that was last year. From its Subetapedia article it happens sometime in November, after Morostide is over and done with.

I think it's related to Guy Fawkes Day. I've seen some items that suggest that. Therefore, it should be around the fifth of November.