Use system date & time format
Fractal currently uses it's own date & time format when displaying the timestamps on messages. This can be very different from what the user's settings are. For example, in GNOME a time would be displayed as "Aug 2, 6:09 PM". In Fractal, this would be "2 Aug 18:09". Users used to the former format would need to mentally translate the latter as they read through message history due to the inconsistency.