iPhone photos sometimes save the incorrect EXIF:OffsetTime* values

[delerious]

I have a script uses ExifTool to check for inconsistencies in timestamps.

One problem it found with some iPhone 14 Pro photos (I haven't run it on photos taken with earlier versions of the iPhone to see if they also have the problem) is that sometimes the photos will have incorrect EXIF:OffsetTime, EXIF:OffsetTimeOriginal, and EXIF:OffsetTimeDigitized values.

For example, I was in a museum in San Diego's Balboa Park, and I took over 500 photos. About 250 of those photos have the wrong EXIF:OffsetTime* values. San Diego is supposed to have a time zone offset of -08:00, but for those 250 photos, they have the EXIF:OffsetTime* values set to either -07:00, -06:00, or -05:00.

Interestingly, when the EXIF:OffsetTime* values are wrong, the EXIF:DateTimeOriginal, EXIF:CreateDate, and EXIF:ModifyDate values are wrong too. However, if you try to calculate the UTC time from the incorrect EXIF:DateTimeOriginal and EXIF:OffsetTimeOriginal values, you will always end up with the correct UTC time.

For example, if I took a photo at 11:00am local time, that means the EXIF:DateTimeOriginal should be something like "2023-01-01 11:00:00" and the EXIF:OffsetTimeOriginal should be "-08:00". But the photo might be saved with an incorrect EXIF:DateTimeOriginal value of "2023-01-01 14:00:00" and an incorrect EXIF:OffsetTimeOriginal value of "-05:00". But when you calculate the UTC time using those incorrect values, you still get the correct UTC time.

This problem also happened with some photos I took at the San Diego International Airport, which is fairly close to the museum in Balboa Park. But the problem did not happen with any photos I took in other parts of San Diego or any part of Los Angeles (I did not go to any airports in LA).

I wonder if this problem is airport related? Because I noticed the same problem with some photos I took at a Houston airport and a Washington, DC airport.

[Phil Harvey]

I can't help here because I don't know how iPhone determines your time zone.  Is there a setting that allows you to specify the time zone?  It seems like the automatic time zone determination doesn't work very well.

- Phil

[delerious]

Yes the iPhone does have a setting that lets you set the time zone, however mine is set to "Set Automatically", and I do have Location Services turned on, and the Camera app is set to "While Using" for Location Services.

I was thinking this problem maybe had to do with Airplane Mode, because I saw a thread on another forum where someone said their photos taken in Airplane Mode all had the time zone offset set to their home time zone. But that wouldn't explain this problem, because my photos are tagged with 4 different time zones. And my understanding is that GPS will still work if your phone is in Airplane Mode.

Another thing to note is that the iPhone 14 Pro I used doesn't have any cellular service. But again, GPS should still work without any cellular service.

I guess the GPS time was just inaccurate near those 3 airports for some reason? At least the GPS coordinates are accurate - I plotted the Composite:GPSPosition value on a map for one of the photos from the museum with an incorrect time zone offset, and it showed me the correct museum in San Diego.