Steps to reproduce:

1. Add new/Update existing SLA form
2. Go to Excluded downtimes tab, add an excluded downtime
3. Add another excluded downtime with identical start time, but in the end add seconds as well
4. Observe in excluded downtime table seconds are not displayed, periods are identical, no seconds displayed
5. Click edit for the period you added seconds to - observe no seconds in form field; cancel editing of period
6. Observe no inline error that periods must be unique is displayed
7. Add/Update the form, observe form saved successfully

Actual: identical expected downtime periods are allowed

Expected: added seconds are ignored/cleared before saving, no identical periods allowed

Example: