Day One offers four different views for your data. You can view your Timeline, Photos, Maps, and Calendar. Each one offers a different perspective on looking back on your memories.
The view options are along the bottom of the app. Each one is a tap away.
There are now options in the Photos view to start a new entry from the Photo Picker or camera at the top. Near the bottom, there are filters for Photos, Video, and Audio entries.
Using the Calendar view, you can view past entries or scroll to a date to create entries on past or future days. See here.
While scrolling through the Timeline, Photos, or Calendar view, you can tap on that icon a second time to quickly scroll to the current date.