fixes https://github.com/TryGhost/Team/issues/1946
Problem:
- When running the admin tests in a timezone that is later than UTC, the tests failed.
Causes:
- Some tests needed some adjustements
- The DateTimePicker did not always use the correct timezone.
- Test models createdAt times sometimes depended on the timezone of the test runner
Solution:
- All the input DateTimePicker gets should be processed in the blog's timezone.
- Make sure that all communication (properties, setters, minDate...) with `PowerDatepicker` happens in the local timezone. When setting, convert that date to the blog timezone and use that as the real value.
07cb542b97