Which is how we get the October revolution in November.
The leap second is because the Earth's spin varies. The orbit isn't varying significantly, it's just not a whole number of day-night cycles which is inconvenient for us, but the spin actually varies. To "fix" this variation we have leap seconds. But unlike the very noticeable October versus November difference, a century of missed leap seconds adds up to much less than a minute of difference between solar time and civil time, and that's not something you'll actually notice.
In contrast leap seconds are not predictable because they're trying to smooth out spin variation and the planet's spin is affected by natural processes. The IERS measures UT1 and we add (or remove) leap seconds to make UTC try to approximate UT1, we get a few months warning at most that a new insertion or removal is needed.
And despite being very difficult all of this is also pointless because we don't care. As an astronomer you know you don't try to use a wristwatch to figure out the Earth's rotation, you can just look that up online and use your exact position. But for any other purpose except astronomy we don't need this angle information, we want a nice regular time and the atomic time, TAI, already provides that without this nonsense about leap seconds.