[BUG] case timeline date badge off by 1

[jasonwuwrf]

Describe the bug
The badge that is on the left side, in column 1, seems to render in the date prior to the first event of the date. The case timeline is in UTC. The date and time for events are showing in UTC. The outcome does not seem to be impacted by the offset provided, since the bug seems to be related to date the after conversion to UTC has occured.

To Reproduce
Steps to reproduce the behavior:

1. Go to a case timeline
2. Add events to the timeline, using any UTC offset, including -00:00.
3. Show the timeline
4. See error where the date badges are off by one

Expected behavior
The date badge should be equal to the displayed date(time) in the first event in the list. It is confusing to see the "day before" the first event showing and can lead to misinterpretation of the events at a macro level.

Screenshots

[slw07g]

This is because a known inconsistency with the js Date() constructor.
Currently, a date string is passed to the constructor ("yyyy-mm-dd"); one way to work around the issue is to pass the year, month, and day separately. When doing this month needs to be set to m-1, because Date expects months to be numbered starting with 0 instead of 1.