Java 9 had some improvement in
Long story short,
Clock.systemUTC().instant() creates an
Instant object using nanoseconds instead of milliseconds.
This causes some change in
Instant.now() in Java 9 or higher.
In Java 8,
In Java 11 (9 or higher),
So if your code relies on
Instant.toString(), it may not work the same as before upgrading Java from 8 to 9 or higher.
By the way, relying on
Instant.toString() is bad so if you have code like that,
now is the time to fix it.