All those confusing dates and times

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There are many date/time fields associated with photos and videos, governed by overlapping industry standards that have evolved over the decades. The names that LR and other apps use often differ from the industry-standard name of the underlying metadata field, and the names vary across apps. So it's quite understandable that users get very confused by this mess.

Here is my understanding of these fields and how LR interprets them:

LR Field: Default > Capture Date/Time
Metadata Fields: EXIF: DateTimeOriginal, IPTC: DateCreated, XMP: DateCreated
File Explorer: Date Taken
Finder: <none>
Description: When the shutter was pressed. LR reads the capture date from one of the metadata fields, using fairly complicated rules specified by the Metadata Working Group standard. If the photo file is missing all of the capture-date metadata fields, then LR will use the file's current Date Modified but in an inconsistent, buggy way, and every time the file's Date Modified changes, LR will update the displayed Capture Date/Time automatically. To avoid this bizarre behavior, use the command Metadata > Edit Capture Time to assign a capture date to the photo.

LR Field: EXIF > Date Time Original
Metadata Field: EXIF: DateTimeOriginal
File Explorer: Date Taken
Finder: <none>
Description: Displays the EXIF field DateTimeOriginal (industry standard capture date, when the shutter was pressed). If this LR field is blank, that means the photo probably doesn't contain a capture date in its metadata (though there are other, lesser-used industry standard fields that might contain capture dates -- see above).

LR Field: EXIF > Date Time Digitized
Metadata Fields: EXIF: DateTimeDigitized, IPTC: DigitalCreationDate, XMP:CreateDate
Description: When the image was converted to digital form. For most digital cameras, EXIF: DateTimeDigitized will be within a second of EXIF: DateTimeOriginal; for scans of analog pics, EXIF: DateTimeDigitized should be the date of the scan, while EXIF: DateTimeOriginal is when the shutter was pressed on the film camera. Some scanning apps will set EXIF: DateTimeDigitized, but many don't.

LR Field: EXIF > Date Time
Metadata Fields: EXIF: DateTime, XMP:ModifyDate
Description: When a standards-conforming app last modified the image or its metadata. LR displays this field but, contrary to the standard, doesn't update it in the photo file. The name of the field is the source of much confusion, since people naturally assume it's the capture date.

LR Field: EXIF and IPTC > Metadata Date
Metadata Fields: XMP:MetadataDate
Description: When a standards-conforming app last changed any metadata in the photo file. For cataloged photos, LR changes this field only when it writes metadata back to the file via the command Metadata > Save Metadata To File or via the option Catalog Settings > Metadata > Automatically Write Changes Into XMP. For exported photos, LR will set the field to the time of export.

File Explorer: Date Created
Finder: Date Created
LR Field: <none>
Metadata Field: <none>
Description: The time that the original file was created by the camera or operating system. For files produced by cameras, Date Created is usually within a second of EXIF: DateTimeOriginal. Decades ago, most Mac apps preserved Date Created as a file was copied or modified. But today many Mac apps and utilities (including Lightroom and some Apple apps and utilities) will not preserve Date Created when a file is copied, modified, or exported. On Windows, Date Created is almost always set to "now" whenever a file is copied or modified (good backup utilities will preserve it). Many Mac users get very frustrated when they learn that LR is changing Date Created and doesn't preserve Date Created in exported photos, especially since Apple has never deigned to include capture date as a Finder column. But if you care about preserving capture dates, use the industry-standard metadata field EXIF: DateTimeOriginal (LR Capture Date) -- don't rely on Date Created!

File Explorer: Date Modified
Finder: Date Modified
LR Field: <none>
Metadata Field: <none>
Description: The time that the original file was last modified by the camera or operating system. For files produced by cameras, Date Modified is usually within a second of EXIF: DateTimeOriginal. LR modifies a file when it updates the file's metadata or when it moves a file between volumes, The Date Modified of exported files will be the time of export.

Photo Time Zones

Believe it or not, until relatively recently, the EXIF standard didn't provide a way to record the time zone of the capture date. Even now, most cameras don't record the time zone.

So LR ignores any recorded time zones in the various date fields. A photo taken in London on 1/1/2023 10:00 UTC and a photo taken in New York five hours later on 1/1/2023 10:00 EST will both have their capture dates displayed in LR as 1/1/2023 10:00, even if the cameras recorded the time zones. LR will consider the two capture dates as identical for the purposes of sorting, filtering, and searching.

LR does try to preserve any time zones present in the metadata date/time fields. I haven't investigated this very closely, since most apps and services still ignore time zones.

Video Time Zones

Most videos produced by phones and digital cameras are encoded in the Quicktime format (or the MP4 format, which is nearly identical to Quicktime). The video capture date is recorded in a Quicktime metadata field. Unfortuately, Apple defined the standard poorly, requiring capture dates to be recorded in UTC (GMT).

But most non-phone cameras record capture dates in local time (whatever the camera clock is set to). So for all cameras except Apple devices, LR interprets the Quicktime capture date as being in the time zone of the computer running LR ("local time"), not in UTC. This will result in incorrect, shifted LR capture dates for Android devices and other cameras that have a notion of time zone and strictly obey the Quicktime standard.

Apple devices record video time zones in a non-standard Quicktime field, which LR reads. So LR will display the correct capture times for Apple-produced videos.

While some other devices also record video time zones in non-standard fields, LR doesn't read those fields. Technically, it's trivial to do so, but Adobe has a unique, conservative legal policy of not reading "proprietary" fields without the permission of the manufacturer. Getting such permission is relatively expensive and involves the legal departments of both Adobe and the manufacturers, and clearly Adobe doesn't view it as worth the effort.

The Mac and Windows Date Modified and Date Created fields are represented internally as UTC (GMT) date/times, so they have no ambiguity about time zone. Often, if a video is missing capture date in its metadata, or LR interprets the Quicktime capture date incorrectly, the Date Modified or Date Created fields will be the same as the true capture date.
 
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John, thanks for the research work and nice summation. Photographers need to know this, and it can be very confusing.

Sometimes I go in Raw Digger, Bridge or LR expanded fields and stare at all the date/time fields in the metadata and EXIF data and am amazed at all the various listings for date/time.

I know some pros want various jpeg creation dates but all I'm ever interested in is the original capture time and date. I don't care when I edited, exported, saved, reedited, resaved, resized, converted it or anything else that happens after original creation. I just care when the trigger was pulled creating the original raw in camera.

Edit later - Are you saying LR messes with my original capture date / time? I want that to never be messed with. That is sacred information.
 
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Are you saying LR messes with my original capture date / time? I
If your photo files contain the capture date in the standard field EXIF: DateTimeOriginal, as nearly all photos from modern cameras do, LR does an excellent job of preserving those capture dates.

It's only for photos that are missing capture dates in their metadata that LR is horribly buggy and weird, e.g. scans and photos downloaded from web services that love to strip metadata. The best thing to do with those photos is use the Edit Capture Time command to "fix" their capture dates, effectively assigning the dates to EXIF: DateTimeOriginal:
https://community.adobe.com/t5/ligh...ion-changes-capture-date/m-p/13474588#M306248
 
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John, Thanks for an excellent explanation.
 

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Thank you for the very helpful info. John.

Isn't the reason that LR doesn't update the EXIF: DateTime and XMP:ModifyDate fields because it is a non-destructive editor and doesn't ever modify original files?
 
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Isn't the reason that LR doesn't update the EXIF: DateTime and XMP:ModifyDate fields because it is a non-destructive editor and doesn't ever modify original files?
When you do the menu command Metadata > Save Metadata To File, LR will write metadata from the catalog (including the capture date) back into the photo file (if it's non-raw, e.g. a JPEG) or the .xmp sidecar (if it's raw).

There is an obscure option, Catalog Settings > Metadata > Write Date Or Time Changes Into Proprietary Raw Files, which does exactly what it says. I've never heard from anyone on the forums who uses that option, but I'm sure at least some people use it.
 
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There is an obscure option, Catalog Settings > Metadata > Write Date Or Time Changes Into Proprietary Raw Files, which does exactly what it says. I've never heard from anyone on the forums who uses that option, but I'm sure at least some people use it.

That doesn't appear to be working (LrC 12.1 on Monterey 12.6). I've tested it a long time ago and it did appear to work correctly back then, but testing it today the date/time change is only being recorded into the XMP sidecar file, not into the original raw.
 
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Need to change that to "doesn't appear to be working in all cases", as I've found that in some cases it does work, other cases it doesn't. Specifically it worked on an ORF (E-M1 MkII), but didn't on a CR3 (R5).
 
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It looks like the problem is restricted to the CR3 file format. I've tried various file formats, including CRW and CR2 from Canon, but only the CR3 format (from 4 different camera models) does not get correctly updated.
 
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It looks like the problem is restricted to the CR3 file format.
Not surprising. Most raw formats are based on TIFF, while CR3 is based on the same container format as Quicktime/MP4, which is completely different from TIFF.
 
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Thanks for this @johnrellis. Very useful but demonstrates the mess that photo metadata is with the multiple schemas. I'm not sure what happened with the Metadata Working group (site seems to be down) that was trying to bring some sanity to this. I've started to use the MWG tags in EXIFTOOL to set fields.
The site went down almost four years ago. Phil Harvey (Exiftool) tried to get more information at the time but got little info. His primary contact at Adobe re MWG had left the company:
https://exiftool.org/forum/index.php?PHPSESSID=a0b4877a40dacfd1e8859fcda2e2f9c0&topic=10030.0
https://exiftool.org/forum/index.php?topic=10908.new;topicseen#new

You can still download the spec from the Internet Archive (see the second thread; I've got my copy stashed away).
 

PhilBurton

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I just managed to download a copy of this spec. However, because of the copyrights I am not allowed to upload a copy to share on Dropbox or similar service.

1674330044255.png
 
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