It is amazing that this even needs to be said. When you are on a date, you have just entered the “holy of holies.” Show some respect. Unless there is a serious emergency brewing (in which case, it could be argued to leave dating until the crisis in under control), your phone and other electronic devices should be closed. Even if your date steps away to go to the restroom, it may still be best to use the time to reflect and not automatically reach for your phone.