clock: update tests to v2.4.0 (#1629)
clock: update tests to v2.4.0 (#1629)

Fixes #1618
* Updated test suite to test for exactly negative 1 hour.
behrtam/xpython,N-Parsons/exercism-python,jmluy/xpython,smalley/python,N-Parsons/exercism-python,smalley/python,exercism/python,exercism/python,exercism/xpython,jmluy/xpython,behrtam/xpython,exercism/xpython