Congratulations, you've successfully reinvented the Egyptian civil calendar, complete with the intercalary holidays and all. Literally the only change is to add weeks. And yes, it did work really well, especially since the feast could add or lose a day to adjust to a known reference (the rise and fall of the Nile in their case). I second this proposal to go back.

Sounds a lot like the French Revolutionary Calendar: https://en.wikipedia.org/wiki/French_Republican_calendar#Months

It actually does account for keep years. https://en.m.wikipedia.org/wiki/International_Fixed_Calendar

What's the work schedule

Weeks should have ten day weeks, and each month should have 3 weeks.

Here's why I'm going to say no. It's because businesses would just rip us off by turning the working week into 8 days and just retaining the 2 day weekend.

No, and double no.

What names shall we give the new weekdays? Because I was thinking maybe we should rename a few existing ones, so no weekdays start with the same letters. Then they can be abbreviated to their respective first letters.

Weeks should have ten day weeks

And instead of calling them "weeks", we could call them by the much more self-explanatory term "tendays".

summer/winter solstice and the spring/autumn equinox as well as new years day are special holidays that fall between months and interrupt the week cycle

You can simplify it a little bit by putting the intercalary days between months, rather than using them for the solstices. We can put Midwinter between January 30 and February 1 and Midsummer between July 30 and August 1, in the northern hemisphere.

For the sake of putting it in a more user-friendly location, our leap day should be in the summer for the northern hemisphere (where most of the population is). So put it the day after Midsummer.

The only thing I would do differently from the Calendar of Harptos is that, like you, I would use New Year's Day as the 5th annual intercalary day.

The 365th day is new years day... duh.

This is what I want! Fuck, this has it all! Its beautiful!

Current workforce is schedule around a 7day centric week. It's far easier to reorganize where the weeks fall in the year than changing the structure of a week. Suddenly the workforce would have segment of work overlapping between weeks, it's an organizational nightmare.

The international fixed calendar did propose a solution for the 365 days and leap year but it's basically out-of-the-week holidays.

I don't see why 7 day weeks are bad in regard to the number system. We rarely need to divide the days of the week into equal portions. Remembering 1, 8, 15 and 22 as mondays would be trivial after a while.

You also claim that failure to address the 365th day and leap years is an issue, but your proposal also includes several cycle-breaking days. So the same issue would persist.

Moon deviation isn't something I really worry about, but having a period which almost align with the cycle seems useful. It would be easy to just examine the initial phase within the month to chart out the rest of the month.

However, I think the biggest flaw is that the calendar would be divided into 13 equal parts, which sucks to divide into typical use cases, i.e. into 2 parts. You could split the 7th month, but it's not really elegant. Dividing the year into 3 or 4 parts would be a mess.

Any solution that has some form of "oh those days? Nah, we don't count those" is disqualified immediately in my book.

Weeks should have a prime number of days. It’s not wise to be dividing weeks up.