If your phone is turned off, e.g. because the battery is flat, your tado° is no longer able to receive any further changes to your location. In this case, tado° won’t adjust or switch between the Home and Away modes. This means that the Smart Schedule will remain in the mode that was active when the mobile device lost power.
To prevent unnecessary energy usage, tado° will default into Away Mode if the location information for all users is older than 48 hours.