In 2009 Tantek Çelik
published a draft of a
new calendar with 5-day-weeks solving issues with the Gregorian one.
I am not convinced, that this is a useful way to re-structure the calendar.
Back in the days we set up a calendar for our RPG world together with Sebastian Gerstl and Markus Biedermann,
which makes transition much smoother. We came up with this concept: