Chris Wilson from GGG did a talk a few years ago regarding among other things long term player retention. I linked the video at the end of the post with the timestamp. He points out its important for the players to know where new gameplay cycles begins so they can plan around the date. I believe that's paramount to this game health.
>https://www.youtube.com/watch?v=pM_5S55jUzk&t=1209s