The Fusion bases displayed time/date on the time and date set on the phone/tablet the Fusion is connected to. Each time the Fusion is reconnected with the Striiv app, time and date are updated. To reconnect the Fusion, simply double tap the Fusion with the app open. If that doesn't do the trick, you'll need to force quit and restart the app, then double tap the Fusion with the app open.
If tapping the gear icon on the gray device banner at the top of the app home screen does not show device info, the Fusion will need to be factory reset in order to re-pair with the app:
Turn on the device and swipe to the left of the time/date (and battery percentage) screen to select Apps > swipe to the second Apps screen to select settings > swipe to the factory reset screen and tap the check mark to confirm.
Either a 4 digit pairing code or striiv.com/start will then appear, which signals your device is ready to be paired through the following process: https://www.striiv.com/pages/set-up-your-tracker