Fix time format validation

[justin-tay]

Closes #1187

Fixes the time format validation and adds the appropriate unit tests.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.33%. Comparing base (48ca3c2) to head (c9158a6).
⚠️ Report is 95 commits behind head on master.
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1188      +/-   ##
============================================
- Coverage     78.90%   78.33%   -0.58%     
- Complexity     1965     2082     +117     
============================================
  Files           172      201      +29     
  Lines          6352     6877     +525     
  Branches       1255     1259       +4     
============================================
+ Hits           5012     5387     +375     
- Misses          867     1019     +152     
+ Partials        473      471       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.