If you have a FB account and can view the page logged in, mouse hover over the date and it will give you the exact hour:minute it was posted to FB.
https://www.facebook.com/mark.sievers.1
1st post: 6/30/2015 7:28pm
last post: 7/12/2015 4:45pm
6 in between.
ETA: I'm Central time and may need a person in Eastern to confirm if another one hour adjustment needed. I'm pretty sure I see things in my time zone. FYI.
