Photos being imported into Apple Photos with modified date rather than creation date

The dates I am referring to I am viewing through the "Get Info" feature on macOS

There are two kinds of metadata involved when you consider jpeg or other image file.

 One is the file data. This is what the Finder shows, and which is shown in the Finder's Get Info. This tells you nothing about the contents of the file, just the File itself. The problem with File metadata is that it can easily change as the file is moved from place to place or exported, e-mailed, uploaded etc.

Photographs have also got both Exif and IPTC metadata. The date and time that your camera snapped the Photograph is recorded in the Exif metadata. Regardless of what the file date says, this is the actual time recorded by the camera. Photo applications like Photos, Lightroom, Photoshop etc get their date and time from the Exif metadata not the file date.

The problem is that the Finder doesn't work with Exif.

What does the Photos app report as the dates? And are you sure the Exif hasn't been stripped from these files, something that can happen with images sent via iMessage and similar fast messaging apps?

iStephan wrote: Yes apologies when I said Get Info, this is actually where I was looking. The "Creation Date" is the correct date when the photo was taken, and my understanding is that this is the date that Apple Photos should assign when a photo is imported. Instead, my library is assigning the "Modification Date".

So, you're using Preview rather than Photos? Is that correct?

Photos and Preview don't "assign" dates-- they use the dates in the metadata. Photos copies the "create date" to its database, and that's what you see in the Info Window of Photos. The database value can be changed, but the original file isn't altered.

If your pictures are in Photos, try doing a File>Export>Export Unmodified Original to place a copy of the picture file in a folder someplace, and then examine it with the free ExifTool Read that Keith Barkley and I suggested. You can get that from either the link he provided or from the App Store. See what dates are there. Here's an example:

By "Whenever I import a photo into Apple Photos on my Mac," what do you mean? Do you use the File>Import menu, or some other process?

Where do you see these dates? If you save a picture in Finder, what do you see? You didn't tell us what OSs you are using, and Finder treats picture files differently in different versions. In older versions, Finder only showed the file dates, since Finder is a File Manager. That seemed to cause some confusion, so in newer OSs, Finder shows the image creation date, and in Tahoe Finder shows the image modification date, as well. But Photos and Preview always show the Image information rather than the file information, if it's there in the picture's metadata.

Photos arriving through Messages and email may have their information stripped for privacy issues. This can depend on how the picture was loaded into the sender's own Message app or into their email app.

If you have a picture in Finder, you can look at the Exif metadata with the free "ExifTool Reader" (not Pro) available for free in the App Store.

Open one of the affected images in Preview

Go Tools Menu -> Show Inspector. In the Inspector click on the lower case I button and note the heading for Exif. What does that show as Date Time Original and how does that compare with the date and time in the Get Info window?

You can always try a new library as a test.

I suggest you use ExifTool to view the EXIF data before import.

https://exiftool.org/