Fix time format validation

[justin-tay]

Closes #1187

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

[codecov-commenter]

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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.
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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 

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