I recently wanted to copy a large set of photos (over 10,000) out of Apple Photos (Mac-based photo management application/database) and save them on a USB hard drive so I could import them to Google Photos (cloud-based photo management service).  I did an export of all the photos out of Apple Photos, which saved the date and time information in the EXIF metadata, but not in the file metadata itself.  Here’s how I solved this (which I’m sure isn’t the most elegant solution), using a Mac:

1. I found this thread, which explains how to use a few different tools to accomplish this, on photo.stackexchange.com
2. I downloaded jhead for my Mac
3. jhead for the Mac doesn’t support recursive (e.g. -r) calls, so I needed to consolidate all the images from sub-folders and sub-sub-folders — I did that using this command on the Mac terminal using this command “find ./ -name ‘*.jpg’ -exec cp ‘{}’ ./ \;“, which I found on this forum http://ubuntuforums.org/showthread.php?t=1385966:
4. Then I deleted the folders and sub-folders, as I don’t need them for organization (I just want to get the photos backed up into Google Photos)