Airplane Mode and iPhone's Correct Time ?

[pmcjr]

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.

 

[Weaselboy]

Airplane mode turns off all the radios, so there is no need to also turn off cellular.

I know when I fly across time zones in airplane mode, the time is always wrong when I land until I turn airplane mode off and the phone grabs the cell. signal again and the time zone is adjusted.

 

[pmcjr]

Airplane mode turns off all the radios, so there is no need to also turn off cellular.

I know when I fly across time zones in airplane mode, the time is always wrong when I land until I turn airplane mode off and the phone grabs the cell. signal again and the time zone is adjusted.

Thanks, Weaselboy. That makes sense and confirms what I thought...the correct time comes from a cellular carrier's signal. You don't get that in Airplane Mode. So, if you're out of the country and leave the phone in Airplane Mode and don't want to turn it OFF in order to avoid cellular or roaming charges, even for a minute to two in order to grab a cell signal, your phone would not adjust to the local time? If you did turn Airplane Mode OFF, I'm assuming a foreign carrier's signal would give you the time adjustment even if you still have a US Sim card...or not? You can adjust the time manually, though, in the foreign country by going to Setttings>General>Date and Time. That might be the safest best if you want to keep Airplane Mode ON and just go with Wi-Fi. Would you agree?
THanks.

 

[Weaselboy]

Thanks, Weaselboy. That makes sense and confirms what I thought...the correct time comes from a cellular carrier's signal. You don't get that in Airplane Mode. So, if you're out of the country and leave the phone in Airplane Mode and don't want to turn it OFF in order to avoid cellular or roaming charges, even for a minute to two in order to grab a cell signal, your phone would not adjust to the local time? If you did turn Airplane Mode OFF, I'm assuming a foreign carrier's signal would give you the time adjustment even if you still have a US Sim card...or not? You can adjust the time manually, though, in the foreign country by going to Setttings>General>Date and Time. That might be the safest best if you want to keep Airplane Mode ON and just go with Wi-Fi. Would you agree?
THanks.

Yeah... that's what I would do. But I really don't think it would even pick up the time from another carrier without their SIM, but I'm not sure about that.