If you build your family tree on your family site online, please read the following article: How do I add a date to a photo on my family site?
1. Open your family tree in Family Tree Builder.
2. Click on the ‘Photos’ button.
3. Double click on the photo to open the 'Edit Photo' window.
4. Add the date, using small calendar icon and click ‘OK’.
5. Save your tree and sync it with your family site.