It looks one bug in java.time.OffsetDateTime. The return value of compareTo() and OffsetDateTime.INSTANT_COMPARATOR.compare() are different.

Sample code:
========
OffsetDateTime a = OffsetDateTime.of(2008, 6, 30, 11, 20, 40, 4, ZoneOffset.ofHours(2));
OffsetDateTime b = OffsetDateTime.of(2008, 6, 30, 10, 20, 40, 5, ZoneOffset.ofHours(1));
System.out.println(a.compareTo(b));
System.out.println(OffsetDateTime.INSTANT_COMPARATOR.compare(a, b));
========

Output:
========
-1
1
========

It does not makes sense. The correct value should be a<b.

And it looks the implementation of INSTANT_COMPARATOR is incorrect:
=========
public static final Comparator<OffsetDateTime> INSTANT_COMPARATOR = new Comparator<OffsetDateTime>() {
    @Override
    public int compare(OffsetDateTime datetime1, OffsetDateTime datetime2) {
        int cmp = Long.compare(datetime1.toEpochSecond(), datetime2.toEpochSecond());
        if (cmp == 0) {
            cmp = Long.compare(datetime1.toLocalTime().toNanoOfDay(), datetime2.toLocalTime().toNanoOfDay());
        }
        return cmp;
    }
};
=========

I think we can not compare localTime part of OffsetDateTime directly. It should be convert to Instant firstly. Then compare epochSecond and nanoOfSecond.....