How to organize Photo Library by Date on Mac?

The answer to your question was yes-- "View>Sort>Keep sorted by oldest first' means the date that is shown in the info window. That date is, as Old Toad has said, the Capture date if it's recorded in the metadata, or it's the file creation date if the capture date is empty. As you say, you can add a capture date with "ADJUST DATE & TIME."

I'll tell you that I found ADJUST DATE & TIME to be pretty awkward for lots of scanned pictures with randomly arranged dates. I have used the title field to enter "1982 10 21 Joe and Friends," or, if I'm less sure, "1982 Joe and Friends." If there are several of them, I may make it "1982 10 21 -01- Joe and Friends," etc. And then I sort by title. When I find that I have the date wrong, it's pretty easy to change.

The downside is that titles don't work in iOS. So you have to copy all titles into the caption field, anyway.

What is the source of your photos? If the photos have been taken with a digital camera and you imported them from the camera or a smart phone, they should showing the correct date in the info, Richard mentioned. There might just be an offset, if they have been taken in a different timezone, or if the date in the camera has not been set correctly.

For photos that have been shared with you or photos you downloaded somewhere ore scanned from prints or slides, the date may need adjusting.

When I am adjusting the dates os scanned photos, I am collecting the photos taken at the same time and at the same place in an album (a top level album right below my albums), then drag them into a chronologically correct sequence. Confining them in an album is safer when batch changing the location, the keywords, the titles.

To batch change the date and time I am adjusting the date and time of the first photo in the album, then select them all with ⌘A and run an Apple Script, see: Script: Batch Change the Date and Time to a Fixed Date

This script will copy the date and time from the fort photo to all other selected photos, and increment the time by a fixed amount, between successive photos, so they will remain sorted in the correct order, when sorting them by the date. essentially this command is simulating the batch changing of the date and time from the good old iPhoto, one of the best features of iPhoto that we have lost. The script is only working for top level albums, that I why we need to create the album outside any folder.

If all photos in the album should have the same location and keywords, titles, caption, I am using this version of the script: Script: Lift and Stamp all Metadata from one Photo to All Other Selected Photos

It will lift and stamp all metadata from the first photo to the other selected photos, while incrementing the date by a fixed amount between successive photos.

If the photo doesn't have an EXIF Date Taken it will show the import date instead. This is common with scanned photos and those from websites that strip all EXIF and IPTC metadata from the files.

You can change the EXIF Date Taken by the Image ➙ Adjust Date & Time… menu item: