Looks good, but add a test for equality too please, and one for negative timestamps :-)

@derickr I added the test for equality. But test for negative timestamps failed as there seems to be a bug in instantiating negative timestamps from format (returns false in PHP). Setting a timestamp with microseconds with setTimestamp seems impossible as well, so couldn't write a successful test :-)

php -r 'var_dump(DateTime::createFromFormat("U.u", "1.3")->modify("-5 seconds"));'

There already is a bug report for 'U' with negative timestamps: https://bugs.php.net/bug.php?id=66836

Build keeps failing on other stuff, how do we deal with that?

@wjzijderveld The Travis CI build failure doesn't appear to be related to your code.

TEST 13008/13019 [sapi/fpm/tests/010.phpt]
========DIFF========
016+ idle processes:       0
016- idle processes:       1
018+ total processes:      1
018- total processes:      2
========DONE========
FAIL FPM: Test status page [sapi/fpm/tests/010.phpt]

I wouldn't worry about it.

Merged, after a rebase and a fix