Add ability for EventTile to show relative time instead of HH:MM and use it in Threads List.

[Palid]

Threads list has a requirement of showing relative time according to the rules below, but currently it's not properly supported in the application.
We need to implement the relative time rules and then switch up the absolute HH:MM in the ThreadPanel to use the new, relative time implementation instead without breaking current behavior anywhere else.

Rules for properly displaying relative time:

16:55                 (today)
Oct 6                 (yesterday)
Jan 1                 (past, current year)
Dec 31, 2020          (past, not in current year)