BC and AD dates

[rh144]

Hi All,

I'm very new to exiftool. I am an art historian, looking to manage a small but growing collection of photographs of artworks. I came to exiftool because it looks like a way to assign metadata to images that can withstand inevitable moves between computers, operating systems, photo software, etc. during my career.

What is the best way to associate the BC and AD dates of an artwork's creation with an image file? My understanding from reading the forum is that dates associated with the image file's creation or modification can't go reliably earlier than 1970. Is that right? Is there a tag type that can handle the full range of dates for human (ish) made objects (ideally 3 million BC to the present)?

I have experimented with assigning earlier dates to various tags in various image files. The SubSecCreateDate tag for a jpg photo from a Canon can go as early as Jan 1 AD, but it generates an "Invalid CanonCameraSettings data" error. The FileModifyDate of a downloaded png can do the same, with no error. I can't get either to go to BC.

Any advice, including of the 'you can't get there from here' variety would be helpful. Thanks!

[Phil Harvey]

I might do something like this:

Code Select Expand

> exiftool a.jpg -artworkcircadatecreated="1000 BC"
    1 image files updated
> exiftool a.jpg -artworkcircadatecreated
Artwork Circa Date Created      : 1000 BC


This is part of the ArtworkOrObject structure in the XMP-iptcExt tags.

- Phil

[StarGeek]

My understanding from reading the forum is that dates associated with the image file's creation or modification can't go reliably earlier than 1970. Is that right?

For the FileCreateDate/FileModifyDate tags, that is correct.  And if you think about it, it isn't logical to try and use these tags in this way.  These tags are part of the operating system and indicate when the File was created/modify, not the image.  And you can't have a file created from before computers were invented.

Additionally, these tags are extremely fragile.  They will be lost if you upload to the cloud.  They can be changed depending upon what a program is doing with them.  They should never be depended upon.

What is the best way to associate the BC and AD dates of an artwork's creation with an image file?
...
Is there a tag type that can handle the full range of dates for human (ish) made objects (ideally 3 million BC to the present)?

That... is a good question.

I have experimented with assigning earlier dates to various tags in various image files. The SubSecCreateDate tag for a jpg photo from a Canon can go as early as Jan 1 AD, but it generates an "Invalid CanonCameraSettings data" error. The FileModifyDate of a downloaded png can do the same, with no error. I can't get either to go to BC.

The three main EXIF time stamps, CreateDate, DateTimeOriginal, and ModifyDate, can go as early as 0000:01:01 00:00:00, but they don't include the ability to go before that.

But then, these tags are photography based.  They technically shouldn't be set to a time before the first photograph was ever taken.

Actually, checking over the XMP tag list, there is a group of tags for this purpose.  The ArtworkOrObject structured tag.  This is part of the IPTC Ext standard.  These incllude
ArtworkCircaDateCreated
ArtworkContentDescription
ArtworkContributionDescription
ArtworkCopyrightNotice
ArtworkCreator
ArtworkCreatorID
ArtworkCopyrightOwnerID
ArtworkCopyrightOwnerName
ArtworkLicensorID
ArtworkLicensorName
ArtworkDateCreated
ArtworkPhysicalDescription
ArtworkSource
ArtworkSourceInventoryNo
ArtworkSourceInvURL
ArtworkStylePeriod
ArtworkTitle

And, I see Phil has answered the question while I was typing   So I'm going to just leave it at that.

[rh144]

Thank you, Phil and StarGeek!

I didn't know about the ArtworkOrObject structured tag, and it's exactly what I'm looking for. Searching for it has also led me to other useful discussions on this forum and online.

Thanks too for explaining about the fragility of FileCreateDate and which are the main EXIF timestamps---you've saved me from mistakes I didn't know I was going to make.