Prior to reprogramming the timer, be sure to use a straightened paper clip to gently press the reset button in the tiny hole on the front of the timer until you see the screen change.  Once you see the screen change, the timer has been reset.   

 
The timer does have backup batteries which maintain the settings in the event of a power failure or disruption.  If your backup batteries are still good, you can bring the timer inside to reprogram it.  You shouldn't lose any settings when you bring it back to the transformer.  The Intermatic DT-620 timer uses (2) LR44 button backup batteries that may need replacing if they are very old.  The Tork backup battery is built-in and recharges by plugging it into a functional outlet.  It is not replaceable, so the entire Tork timer will need to be replaced once the built-in rechargeable battery fails to hold a charge over time.

You can elect to replace the timer with a smart plug that works with your smart home system, provided the smart plug physically fits in the transformer and your WiFi is strong enough to reach the area of the transformer.  If you use Alexa or Google Home, we recommend this smart plug as it fits neatly inside the transformer and has been trouble‑free for many of our customers.