Standardizing the time zone of embedded timestamps

Photos and videos out of order?

Apple Photos honours the time zone offsets that iPhones record next to the shooting date (OffsetTimeOriginal and friends, see the timestamps explainer), Lightroom ignores them and sorts by the wall-clock time, and Google Photos derives the zone from the GPS position. Most cameras write local time without any offset, and camera, GoPro and drone video stores its creation date in UTC, as the QuickTime format requires. Shots from one trip taken with a phone and a camera therefore end up out of order, with the videos hours away from the photos taken next to them, and each application sorts the set differently.

The Standardize the time zone of embedded timestamps action gives every file the same offset. It reads each embedded timestamp together with its offset, works out the moment it describes, and writes that moment back as a wall-clock time in the target zone with the matching offset. The moment is preserved; only the way it is written changes: 14:00 at +09:00 becomes 07:00 at +02:00. Once every file carries the same offset, wall-clock order and real order are the same thing, and every application sorts the set the same way, whether it honours offsets or ignores them.

This is a different job from the Adjust actions, which shift a date because the camera’s clock was wrong. If the clock was wrong as well, correct it first, then standardize the zone.

The controls

• Convert embedded timestamps to: chooses the target zone: this Mac's time zone, UTC, a fixed UTC offset or another time zone. With a fixed offset a Fixed offset: menu appears, in half-hour steps from UTC-12:00 to UTC+14:00 plus the odd ones such as UTC+05:45; with another time zone a Time zone: menu lists every named zone. A named zone is applied date by date, so files from either side of a daylight-saving change each get the right offset.
• Timestamps without a time zone offset: decides how a file that carries no offset is read: assume this Mac's time zone, assume UTC, assume a fixed UTC offset (an Assumed offset: menu appears) or leave the file unchanged. Camera stills from a trip were usually taken in the zone of the trip; camera video is usually UTC. When in doubt, check one clip against a photo of the same moment before choosing the assumption for the batch.

The preview

The DT Original, DT Digitized and Content columns of the file list show each timestamp with its current offset on top and the converted value underneath. The Offset column shows the current offset, or none for a timestamp that has no offset yet, with the target offset underneath in blue. Files that already carry the target offset are shown unchanged in grey and are not rewritten, so running the action a second time changes nothing, and files added to the folder later can be converted with the same settings without touching the others.

What is written

For images, the EXIF DateTimeOriginal and DateTimeDigitized fields with their OffsetTimeOriginal and OffsetTimeDigitized offsets, and the existing XMP and IPTC copies of those dates. For movies, Apple’s Keys:CreationDate, the content creation date and the QuickTime user data date, the fields that Apple Photos, Final Cut Pro and Lightroom read. The movie header’s own creation date is UTC by definition and is left alone; a movie whose only date is that header, as most action cameras and drones write it, shows n/a and is not touched. No metadata block is created where a file has none. The action handles the same file formats as the other embedded-date actions: JPEG, HEIC, PNG, TIFF, DNG and the common RAW formats, and MOV, MP4, M4V and the other QuickTime-based movie formats.

Which zone?

There is no wrong choice as long as every file gets the same one:

• This Mac’s time zone, for a library you look at at home. Files that already carry your home offset are already right and stay grey in the preview.
• The zone the pictures were taken in, chosen under another time zone. The wall-clock times then match what the clocks on the walls said, which is how most people remember a trip. Files from several trips need several runs.
• UTC, for archives and for files that other software will process rather than people look at.

After the conversion

Apple Photos, Lightroom and Capture One read the dates once, at import, and keep their own copy. Files that are already in a library have to be re-imported, or the metadata re-read, before the change shows. To make the Finder agree with Photos, run Copy EXIF content creation timestamp to file creation date afterwards; see copying dates.

• Video: Correcting Time Zone Errors in Apple Photos (6m 21s), the camera-clock case that the Adjust actions handle.