I just went to my Facebook page.
I went to a photo I posted on July 26, 2014.
I clicked on the photo.
I clicked on "edit."
I changed the date to July 25, 2014, and could even change the time (it previously had no specific time). I added 3PM.
It now says I took the photo on July 25, 2014 at 3PM. The rest of the photos in that series (all of my dogs) still say July 26, 2014.
Easy Peasy.
Nancy, PLEASE know this!!
ETA: I also went to a post from a few weeks ago, one without a picture, and clicked "edit." One of the choices is to CHANGE THE DATE AND TIME ON THAT POST!