An event is a group of photos that were taken at approximately the same time. When you import photos, Shotwell checks when each photo was taken. It then groups the photos into events.
Choose Events from the sidebar to see your photos organized by date. If you select a month or year from the sidebar, a list of events will be displayed in the main window. Double-click an event to see all the photos that were taken around that time.
If a photo has no embedded date/time information, then Shotwell can't automatically place it in any event. In this case the photo will appear in the No Event view accessible from the sidebar. You can still move the photo to any event you like as described below.
To give an event a name rather than referring to it by its date, select the event, click Edit ▸ Rename Event and enter a new name. Another way of renaming an event is to double-click its name in the sidebar; type a new name and then press Enter.
Even though photos are initially grouped into events by their date, you can move photos between events. To do this, drag any photo to the sidebar and drop it on an event.
To create a new event, select the photos you would like in the new event and click Events ▸ New Event.
To merge events, select Events from the sidebar, then, while holding down Ctrl click on the events you want to merge in the main window area. Finally, click Events ▸ Merge Events.
Events are displayed in a tree in the sidebar, organized by the year and month of the earliest photo in the event. To change the event sort order, click View ▸ Sort Events and select either ascending or descending.
If you select the Events item in the sidebar, you'll see a single photo which represents each event. This is called the key photo.
By default, Shotwell uses the first photo in each event as its key photo. To use a different key photo, select the photo and choose Photos ▸ Make Key Photo for Event.