OffsetTimeOriginal: the time zone missing from EXIF dates

Tag definition

OffsetTimeOriginal is the ASCII ExifIFD field 0x9011. It is distinct from OffsetTime and OffsetTimeDigitized, which accompany different timestamps.

Sources: ExifTool EXIF tag definitions

Convert local capture time to UTC

For DateTimeOriginal 2026:01:12 09:15:00 and OffsetTimeOriginal +02:00, UTC is 07:15:00 on the same date. Subtract a positive offset; add the magnitude of a negative offset. Use a date-time library to handle day, month, and year boundaries.

Do not attach the computer’s current time zone to old camera dates. The photographer may have traveled, and the computer’s current daylight-saving offset may differ from the offset at capture.

exiftool -G1 -a -s -DateTimeOriginal -OffsetTimeOriginal -SubSecDateTimeOriginal photo.jpg

What if the offset is absent?

Report the time zone as unknown. A GPS timestamp or independently documented camera setting may help establish it, but any inference should remain distinguishable from an explicitly stored offset.

An offset of +00:00 is meaningful and must not be treated as empty. Conversely, a missing string is not equivalent to zero. Model these states separately in imports and databases.

Avoid applying an offset twice

Some tools expose a composite timestamp that already incorporates the offset and subseconds. Inspect the field group and the returned representation before doing arithmetic.

Store an original local value and its known offset alongside a normalized instant when your application needs both archival fidelity and sorting. A normalized instant alone cannot explain how the camera represented the time.