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* Add ``shift()`` method to move forward in time by a delta whilst travelling.
This is based on freezegun's ``tick()`` method.
Thanks to Alex Subbotin for the feature in
`PR 27 <https://github.com/adamchainz/time-machine/pull/27>`__.
* Fix to work when either ``clock_gettime()`` or ``CLOCK_REALTIME`` is not
present. This happens on some Unix platforms, for example on macOS with the
official Python.org installer, which is compiled against macOS 10.9.
Thanks to Daniel Crowe for the fix in
`PR 30 <https://github.com/adamchainz/time-machine/pull/30>`__.