I am using sync, yes. It's strange, in my inbox your spoiler format appears correctly as the colons, but in the thread it appears as greater exclamation mark. I think sync is not only using a different tag to make it work, but live changing other users' formatting 🤔.
I checked my post in browser and it was changing the less than sign to the HTML character code do that may also be the issue.
Make it five 6-day weeks and twelve 30-day months, you got yourself a deal. If we want to fit the moon thing like in OP a month needs to be ~29.5 days and 30 would be closest. Twelve months also allows us to keep lining months up with seasons and use quarters for stuff.