As WC said you're confusing Albums in Photos with Events in iPhoto. In Photos Moments are the new Events and are based on date.
There's a way to simulate events in Photos.
When the library was first migrated there was a folder created titled iPhoto Events and all migrated iPhoto Events are represented by an album in the folder.
When new photos are imported into the Photos library go to the Last Import smart album, select all the photos and use the File ➙ New Album menu option or use the key combination Command+N. Name it as desired. It will appear just above the iPhoto Events folder where you can drag it into the folder
When you click on the iPhoto Events folder you'll get a simulated iPhoto Events window.
However, if you want to remove a photo from one album after adding it to another you'll have to go back to the source album and delete it from there.
