Before these tests could be flaky if they happened to be called around
the edge of a second. Now we try up to 5 times to execute the tests
while staying within the same second.
Since years don't have a constant amount of seconds because they can be
leap years no constant will work in all cases. We now test a timezone in
both the positive and negative direction and check that at least one
worked. Assuming years are at least 2 days long this will always pass
at least one test.
