It sounds like your using Photos that came with Yosemite (10.10.5) instead of iPhoto. Is that correct? If so then the following will be relevant to you:
Moments in Photos are the new Events, i.e. groupings of photos sorted by date taken.
Since you're not migrating from an iPhoto library the first sentence below is not relevant. The text in the quote box below is particularly relevant.
When the iPhoto Library was first migrated to Photos there is a folder created in the sidebar titled iPhoto Events and all migrated iPhoto Events (which are now Moments) are represented by an album in that folder. To open the sidebar if it's not already open use the Option+Command+S key combination.
NOTE: It's been reported by several users that if the Event albums are moved out of the iPhoto Library folder in the sidebar they may disappear. It's not widespread but several users have reported that issue. Therefore, if you want to assure that you keep those Event albums don't move them outside the iPhoto Events folder.
There's a way to simulate events in Photos.
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 a folder that you create to simulate the Events view.
When you click on that folder you'll get a simulated iPhoto Events window.
The downside to the simulation is that the Albums/Events can only be sorted automatically by Title. But they can also be sorted manually, either in the sidebar or in the folder's window at the right. This will change with the release of Photos 2 with El Capitan this fall. That will allow the sorting by date or title, ascending or descending.
Tell Apple wha new features you'd like added in Photos via https://www.apple.com/feedback/photos.html.