Q: Since April 2016, my photos don't show up in "moments", only show up in "albums/all photos". I want to make a calendar but can only add photos from "Moments". .  How can I add in my pics to moments or from "all photos/albums?

You are 4 updates behind - you need to upgrade to El Captain OS X 10.11.4 and Photos 1.5 - there are many new features adn bug fixes adn this will probeble resolve thigns

Once you get up to date is you still have issues post back

LN

Control (right) - click on the thumbnail in the album and select Show in Moment from the contextual menu.  That will take you to the Moment that the photo is in:

If " Show in Moment" does not reveal the photo, if you click a photo in "All Photos", your Photos Library may need repairing.

Try, if repairing your Photos Library will help:  https://help.apple.com/photos/mac/1.0/?lang=en#/pht6be18f93

• Important: You should back up your photo library before repairing your library.

 

• If Photos is open, choose Photos > Quit Photos.
• Press Option-Command and double-click the Photos icon in the Applications folder (or click the Photos icon in the Dock).The Repair Library window opens.
• Click Repair to rebuild your photo library.