The only reason Fahrenheit looks like "a human scale" is because you're used to it. At least Celsius has clear reference points (everybody knows how cold is "freezing water" and how hot is "boiling water").
> Doesn't it make sense for some things to divide by 3 and 4, like a year, so that a season is 3 months long, instead of 2.5 months long (as in the old 10-month year system, ending in December)?
Programmers all around the world would first hate you for changing things, and then love you for making a consistent dating system.
But, seriously now, dates are a bit of a difficult system to change. You want to be able to refer to past dates without too much confusion, and also there are outside restrictions such as the length of a year compared to a day (not many integer divisors of 365 days).