At first ensure that your devices are placed near to each other – this is necessary for correct interaction between them. Then open «Apple Watch» app on your iPhone.
How to remove synchronisation between Apple Watch and iPhone Press “My Watch” menu in the app, in the bottom of the window, and select “Apple Watch” panel. Then press “Unpair Apple Watch” button. The program will ask for confirmation of cancellation of synchronization between devices, which results in deletion of settings and content of the watch on your smart phone.
Nevertheless, iPhone will generate a backup copy of data from Apple Watch before termination of the process; further your can use it for adjustment of your new hours.
To delete data stored on Apple Watch (to return the device to default settings), open Settings app, select General-> Reset-> Erase all Content and Settings.