The International Fixed Calendar simplifies dates and accounting because every month has the same number of days and every date is the same day of the week. The same calendar can be used every year!
Wikipeadia explains the pros and cons well. Kodak company is famous for having used it for 60 years.
I got tired of having to check the Gregorian calendar every fortnight to keep up with the date of housemate spreadsheets. Keeping this link handy in your phone and computer makes things easy. I adapted the old image (below) to incorporate the Gregorian calendar (above) for easy reference on paper. The watermark shows the Gregorian months (not dates). You’ll notice the months lag behind the IFC in the first half of the year and in the second half they precede because of the extra month in the middle, Sol. The end of the financial year (which in Australia is the 30th of June in the Gregorian calendar) falls on the 13th of Sol in the IFC, because the Gregorian calendar has 181 days in the first half of the year and 184 in the second half. If we used the IFC, the end of the financial year would be the 14th of Sol, exactly in the middle. For both calendars, every year it’s the same. Quarterly periods in the IFC are January 1st – April 7, April 8 – Sol 14, Sol 15 – Sept 21, Sept 22 – Dec 28.
I propose that “Year Day” be a accounting-free day, where everything is done for free, as envisaged by The Free World Charter.