Standardization

Yeah, there are lots of inconvenient things about time, earth, moon and the sun. If you pick a certain length of time, and use consistent multipliers, it’s not going to align with all of these things. Oh, and even if it somehow did, it wouldn’t work forever, because these things aren’t even constant. They drift over the centuries and millennia, so if you memorize that a day is exactly 86400 s, it’s not going to be like that forever.

Also, the Gregorian calendar is very broken, but at least it’s not as broken as the calendars that came before it. It tries to use mathematically pleasing even numbers as much as possible, but that’s just not compatible with reality. Just look up leap days and leap seconds to see what I mean.

The Islamic calendar is an interesting one, because it simply accepts the fact that the solar system is a bit random and wobbly, so the length of a month varies accordingly. It’s not super precise, which is a problem, but at least it’s easy to use even if you can’t do complicated calculations, models and predictions. It also places a lot of importance on the moon, which is nice and practical in many ways, but it doesn’t align with the seasons at all.

If I could make a new calendar, I would just forget about the concept of months, and count the days since the winter solstice. That way, day 123 would be the same every year, and the calendar would be good for tracking season. At the end of the year you may or may not have a leap day depending on random wobbles. If the moon is important to your activities, then you could use any of the many lunar calendars people have already invented.