Date message was posted improved UX.
The date posted is a great addition to the timeline however from a UX point of view I think more detail is required based on time since.
So approx time is ok for that day
3 hours ago
nice and friendly
Probably the same for a few days
5 days ago
But beyond a week the timeline should change to be date specific as there is only so far your brain can understand back in time, for example an instagram image with a date of 23 weeks ago is nonsense, and no one can work out when that was I want to know the date
28th May 2015
Would be much more user friendly.