OffsetTime, OffsetTimeOriginal and OffsetTimeDigitized

EXIF dates carry no time zone, and the three OffsetTime tags fix that. Each holds the UTC offset for one date tag, written +HH:MM or -HH:MM. They arrived with EXIF 2.31 in 2016, so older cameras never write them. Recent iPhones fill all three in their HEIC files.

Each is a 7-byte ASCII string: sign, two digits, colon, two digits, null. The offset describes the clock that produced the date, so 18:42:07 with +02:00 means 16:42:07 UTC. ExifTool applies it in its composite tags:

[ExifIFD]       OffsetTime                      : +02:00
[ExifIFD]       OffsetTimeOriginal              : +02:00
[ExifIFD]       OffsetTimeDigitized             : +02:00
[Composite]     SubSecDateTimeOriginal          : 2026:05:14 18:42:07+02:00

Recovering a missing offset from GPS

If the photo has a GPS fix, the zone can usually be worked out. GPSTimeStamp and GPSDateStamp are UTC by definition, so compare them with DateTimeOriginal:

[ExifIFD]       DateTimeOriginal                : 2026:05:14 18:42:07
[Composite]     GPSDateTime                     : 2026:05:14 16:41:58Z

The gap is 2 h 0 min 9 s. Round to the nearest quarter hour, because real offsets include +05:30 (India) and +05:45 (Nepal); the leftover seconds are just the age of the GPS fix. Compare the dates as well as the times, since an evening shot in New York is already the next day in UTC.

The method assumes the camera clock was right. A clock left on home time gives you the home offset, not the local one. The coordinates tell you which zone the photo should be in, so check the result against them.

Writing the offsets

The EXIF editor has one Time Zone field per date in its EXIF Date & Time panel, and accepts offsets written as +02:00 or -05:00. For a folder of files, ExifTool sets all three at once:

exiftool -OffsetTimeOriginal="+02:00" -OffsetTimeDigitized="+02:00" -OffsetTime="+02:00" photo.jpg

Support on the reading side is uneven: some software honors the offset, some ignores it and shows the bare local time. The guide to changing the date taken has the platform-specific options.