I know that an iPhone keeps the correct time by a combination of GPS location for the correct time zone and cellular data from the carrier for the actual time. I believe this is correct. Am I right? Questions: 1. Will the iPhone continue to keep the correct time across time zones and countries if in Airplane Mode which blocks cellular data? 2. Other posts have stated the importance to avoid roaming and data charges when traveling overseas by using Airplane Mode and Wi-Fi. Other posts have also said to turn Data Roaming OFF. I have noticed that when turning ON Airplane Mode, it does not automatically turn Cellular Data OFF. Is it necessary to also turn Cellular Data OFF in addition to turning Airplane Mode ON and Data Roaming OFF....or is just Airplane Mode ON sufficient? Thank you.