the den calendar is the same as the normal calendar but it has 9 months, the first 8 have 42, making 336 days, and the ninth month, Noden, has 29 days, or 30, depending if it's a leap year or not. If it's not a leap year, then, 29th Noden is a Saturday, if it's a leap, 29th Noden is a Friday and 30th Noden is Saturday. Why? To make the months fixated.
Month 1 - Oniden Month 2 - Biden (bee-den) Month 3 - Triden Month 4 - Quaden Month 5 - Quinden Month 6 - Hexiden Month 7 - Hetaden Month 8 - Octoden Month 9 - Noden Sorry if 6th Oniden looks weird