Can EXIF DateTimeOriginal be treated as UTC if OffsetTimeOriginal is missing?
Asked 11/5/2022
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I'm extracting EXIF capture timestamps from image files. Some images include DateTimeOriginal but do not include OffsetTimeOriginal. If the offset is missing, is it safe to treat DateTimeOriginal as UTC, or should it be considered local time with an unknown timezone? I'm also wondering whether older cameras commonly stored only the user-set clock time without any timezone information.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
3y ago
2 Answers
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Other than the GPS timestamps, EXIF timestamps are supposed to be set to the local time where the image was taken. The three EXIF OffsetTime* are relatively new, having only been added in EXIF 2.31, 2016, while the EXIF standard itself dates back to 1998. And the OffsetTime* tags didn't receive widespread support until around 2019-2020.
Camera phones are the most likely to support the OffsetTime* tags, as they know what time zone they are in. DSLRs usually don't have GPS data without a an GPS accessory, so they will not automatically know the timezone. Most DSLR do have a setting for the timezone and this timezone is usually saved in the camera's MakerNotes.
One thing to note here is that in many cameras (I know Canon and Nikon do this) the Daylight savings is usually a separate ON/OFF setting. The MakerNotes time zone setting is not changed when it is Daylight savings and the time stamp is adjusted based upon the Daylight savings setting.
Originally by user37960. Source · Licensed CC BY-SA 4.0
user37960
3y ago
0
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No. If OffsetTimeOriginal is missing, you should not assume DateTimeOriginal is UTC. In practice, EXIF capture times have traditionally been stored as the camera’s local clock time, and timezone offset tags were added much later (EXIF 2.31, 2016) and only became widely supported around 2019–2020. Older cameras often let users set only date/time, not a timezone, so the value may simply be local time with no offset recorded.
Also, EXIF metadata is not inherently trustworthy: camera clocks may be wrong, unset, or manually altered.
A good approach is:
- read
OffsetTimeOriginalwhen present - otherwise treat
DateTimeOriginalas a naive/local timestamp with unknown timezone - record that the timezone is unknown in your app/UI
GPS timestamps are a separate case and are typically UTC. Some cameras may also store timezone details in manufacturer-specific MakerNotes, but that is not a general EXIF guarantee.
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AI3y ago
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