Implement the International Fixed Calendar and use it

Hi,

Well, this is probably wishful thinking but i wanted to throw it out there to let you folks know.

It's already well over 100 years ago that far superior calendar proposals have been made to replace the defunct Gregorian calendar. There seem to be 2 leading contenders [1, 2] where [2] very nearly made it to the new calendar sometime after world war 2! Just to show that this stuff isn't nonsense. It will change sooner or later as the Gregorian calendar is just terrible inconvenient.

For instance, in [1] i can say "make an appointment on the 5th next month" and i will easily remember that the 5th is a Thursday as every 5th is.

Both calendar proposals are compatible in years with Gregorian as both use the same leap year rules. Personally, i find that to be a flaw but i can see why that inconvenience would be preferred to keep to stay backwards compatible with Gregorian.

Right now, QDate is internally implemented in Gregorian. That can change to the [1] where you have 13 months and each month is exactly 28 days. That eases calculations. See [1] for the rules on leap year days and world day.

My suggestion is to implement QDate internals as [1].
To go from [1] to Gregorian would merely be executing a conversion formula.

Funny perk. Every month would get a Friday 13th

Eventually there should be classes to expose calendar specifics, like world day. But right now it is sufficient to merely have the back end work with either 1 or 2 and to the public expose QDate as-is which internally would convert the given date.

[1] https://en.wikipedia.org/wiki/International_Fixed_Calendar
[2] https://en.wikipedia.org/wiki/World_Calendar