The only difference is the same photo will be tagged in different time zones, so effectively have different time/date stamps.
Are the times wrong, or only differing in the way the time is written, like 09:00:00 UTC would be the same time as like 10:00:00 UTC+1
I found that iPhoto will always display the time in the system time currently set for the mac that is importing the image, regardless of the timezone set, when the photo was captured. But if the timezone was set correctly in the camera and the date has timezone tags associated, the actual time will be correct.
And when importing from an IOS device, the device will use the location data from its current location, when the images are downloaded, not from the location it was in, when the image was taken, if they are different. So I usually try to retrieve all photos from my iPad and upload to the photostream, while I am still in the same timezone.
That is interesting, so are you saying that it the photo was taken in Time Zone A, then imported to the Mac via usb in Time Zone B, iPhoto will tag the photo with Time Zone B?
I noticed that in two situations:
- when importing to iPhoto from iDevices (iPad) with location service enabled in the iPad using USB (the iPad seems to interpret the timezone of the photos as the timezone of the new location)
- when importing from a camera with a different timezone setting. If the dates don't carry timezone tags, iPhoto will assume that the timezone to be the current system time. The results may differ, depending on the kind of timezone setting the camera supports and whether importing directly from the camera or from the card.
When I am travelling between timezones I usually take a picture of a clock at the beginning of each event to be able to check the timestamps after importing the event to iPhoto or Aperture.
Aperture allows more control over the interpretation of timezone settings, btw.