> POSIX is a ``standard'' designed by a vendor consortium several years ago to eliminate progress and protect the installed base.


No, POSIX is an attempt to bring some sanity to the installed base of human calendars.  The established standard tell's us that a year is 365 days.  Wait, every 4-th year is 366 days, except some other rule every 400 years.

POSIX says: fine as long as we can enumerate all YYYY-MM-DD's, we can live  with it.  But the line is drawn where each day is divided into 86,400 seconds.

The problem is that unlike ancient astronomers who were finding better and better approximations to the ratio of two Earth's rotation periods (around the Sun and around itself) every few hundred years, modern astronomers will tell us how many seconds there will be in any given year with only a six month notice.