Try running the unit tests with:
LANG=en_US.utf8 python3 -m unittest
Setting the GRAMPS_RESOURCES environment variable is no longer necessary.
The reason for setting LANG is that some tests compare the output with a file generated using the US locale. This may possibly also fix your time related issue.
I also had a test fail when I had set a non-default name format. This ideally needs to be fixed in the unit test.
Installing CliMerge and ExportRaw is a good idea. You will get more tests to run, but they should just get skipped if these addons are not installed.
Update:
The command I actually use is:
LANG=en_US.utf8 python3 setup.py test