> I do not think the problem is in the JDK. Apparently, we had some weird timezones in the Netherlands before World War 2.

You definitely had But the problem is not limited to Netherlands, it also shows up with Europe/Paris and Europe/Oslo, though with a different breaking point (around 1895 for Oslo).

Note that I'm not saying there's a problem because the result of the conversion by the JDK is different from what I expect.
I'm saying there is a problem because:

1. The result of the conversion when using java.time is different from the result of the conversion when using java.util (Calendar, ...).
2. Even if java.time was wrong, there's still a problem in java.util because a round-trip conversion (to milliseconds since the epoch and back) sometimes does not produce the original value.

Anyway, I'm not saying that to avoid changing the code in Hibernate ORM. Changing the way we do conversion seems to work around the bug, which is why I submitted a PR.