php – Why does DateInterval lack weeks, quarters/seasons, as well as decimal/float versions of each property?

This has puzzled and frustrated me for years: https://www.php.net/manual/en/class.dateinterval.php

y

    Number of years.
m

    Number of months.
d

    Number of days.
h

    Number of hours.
i

    Number of minutes.
s

    Number of seconds.
f

    Number of microseconds, as a fraction of a second.

Where are the weeks and quarters/seasons? In particular, the weeks are sorely missing. In turn, I feel as if I am missing something.

You’d call me crazy if you knew how many hours of my life I’ve plowed into trying to manually calculate the weeks and seasons and decimal versions of all of these based on the existing values, without luck.

I don’t want “rough approximations”, because they fall apart as the two dates drift too far away from each other. “Rough approximations” are easy to make, but I’m looking for exact, accurate information.