Who was the genius who decided that unix time should handle leap seconds? It seems like such an obviously bad idea. The biggest advantage of unix time has always been that it is monotonically increasing and that it is precisely defined as seconds since the epoch, period. And then all of that is now broken because of this decision.
Also, does the problem that the leap second solves actually warrant all of the problems that it causes?
Since Unix time does NOT count the leap seconds, it allows the computation of the human-readable time from the Unix time without knowing when the leap seconds occurred. If knowledge of when the leap seconds occurred is required, then those events would need to be available somehow and used, introducing i) more expensive computation ii) difficulty in future-proofing an app since a reliable and updated data source supplying the times of leap seconds is required.
Some delegates to the ITU-R process have argued in the above fashion. Other delegates have come representing countries which want UTC to remain as a valid count of days in the calendar (for 86400 SI seconds is not the same as one rotation of the earth). For over 10 years these two viewpoints have been at stalemate with no progress toward any compromise that might alleviate the problems that POSIX systems face at each leap second.
I would argue for both fixed UTC based on atomic clocks, and 86400 seconds per day - at the expense of rotation of Earth not being in sync with UTC or calendar boundaries.
It will take 3000 years before leap seconds add up to an hour, but most countries adjust the clocks that much every year for DST. It will take 40000 years before the usual daytime hours turn into night, and by then I hope a single planet's rotation is a historical oddity.
Also, does the problem that the leap second solves actually warrant all of the problems that it causes?