The problem is leap seconds are announced by a committee. There is no schedule of what years will have leap seconds going into the future. This means your time software would have to get updates of which years have them.

I haven't checked them all but I suspect some time software just kludges it and doesn't account for the leap seconds, and the NTP daemon slowly corrects the clock to UTC.

It's a tough situation. The above solution (slow correction by skewing the clock) works fine for most people, but would be death for those who truly need accurate timekeeping -- like astronomers. Having the software get live updates is messy and requires tables for all of history to maintain a true seconds clock. It also means that your date software, when asked, what second is it, will on that magic day return "60" -- when most programs are expecting a number from 0 tl 59. It's been known to break stuff.