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Understanding the date and time tags

There are six common date and time tags in a photo's metadata:

  • Original date/time
  • Digitization date/time
  • GPS date/time
  • Creation date/time
  • Metadata date/time
  • Modify date/time

Each of these six tags has a different meaning, but can often have the same value depending on the context. Typically the original date and time tag is the most significant of the six tags.

Original date/time

The original date and time tag describes the time of the content of the image. For example, and early photograph of Abraham Lincoln reading to his son may have an original date/time of February 9, 1864. For a digital camera, the original time indicates the time the photo was taken.

Digitization date/time

The date and time digitized tags indicates when the content was converted to digital form. For example, the photograph of Abraham Lincoln may have been scanned digitally on February 12, 2002. For a digital camera the digitization date is identical to the original date.

GPS date/time

The GPS date and time tag indicates the time of the GPS position fix for the embedded latitude and longitude. For example, if the photograph was taken February 29th, 2004 at 10:48:22, the embedded GPS date/time may read February 29th, 2004 at 10:48:10 if the embedded GPS position was determined 12 seconds before the photo was taken. PhotoLinker automatically embeds this time when geotagging except in manual mode (where there is no GPS track) or when using time-weighted average points (which aren't real track points).

Creation date/time

The file creation date and time is an attribute tracked by the filesystem and not stored in the standard metadata headers for photographs. In most cases the file creation date should be the same as the digitization date, but inconsistent handling across different filesystems and programs may make this tag less reliable than the other tags.

Modify date/time

The modification date and time tag is embedded in the standard photographic metadata as well as being an attributed tracked by the file system. This tag indicates the last time the file was modified in any way, including editing the image itself or modifying the metadata.

Metadata date/time

The metadata date and time tag indicates the last time a change was made to the metadata associated with the file. In the case where the metadata is embedded directly into the image file, this will be the same as the modification date. However, in sidecar files the metadata may be updates without modifying the file and therefore this date may be more recent.

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