On an iOS device, tap the Profile icon in the top left corner of the app home screen to view your total meditation stats. You can click "My Streaks" to see more detail about your streak history.
On an Android device, tap the menu icon in the top corner of the home screen and select 'Profile' from the side menu that opens to get there. On the Profile screen, scroll below the calendar and tap 'Session History' to see a list of all sessions you've listened to. You can replay previous Daily Calm sessions from the Session History screen as well.