Fix DST issues with generating new shifts
As shown in the master:broken #343503 (comment 709764244), we have some issues with re-generating shifts across timezones.
I'm unsure if this is a spec issue or a bug in the code, but I'm leaning towards the latter.
To fix:
- Ensure we are manually setting dates for these tests and test both
- Changes within a DST boundary
- Changes that cross a DST boundary
We should not rely on current time for these specs.
Edited by Sean Arnold