Lightroom "Time and Date Shift" and how it affects the actual "files"' Time Stamp on my Hard Drive (MacOS)

There are two sets of unrelated date/time fields:

- The filesystem Date Created and Date Modified are maintained by the operating system for every file.  Date Created is set when the file is created, and Date Modified is set whenever the file is changed by a program.

- There are a number of photo date/time fields stored in the metadata section of a photo. The most common one is what LR calls "capture date/time", what the industry standards call EXIF DateTimeOriginal. This represents when the shutter was pressed.

The filesystem date/times and the metadata date/times are completely unrelated.  There is no industry standard that calls for the file Date Created to match the metadata capture date, and most photo programs don't try to make them match (including Apple Photos).  Whenever the programs, including LR, update a photo file, the file Date Modified gets changed, and the file Date Created may change too if the program writes a new version of the file from scratch and deletes the old one (a common programming technique).

For files coming from a digital camera, file Date Created usually matches the metadata capture date (or is within a second or so) because the file was written to the memory card immediately after the shutter was pressed.

In your case, you probably have the selected option Catalog Settings > Metadata > Automatically Write Changes Into XMP.  When you changed the photos' capture dates, LR wrote the changed capture dates back to the photos' files in background.  When LR modifies a JPEG, it usually does so by writing an entirely new file and deleting the old one; thus, you'll see the file Date Modified and Date Created change to "now".

OS X and Windows are similar in their handling of file dates, as is LR running on those platforms.

If you want to make the file Date Created match the metadata capture date on OS X, you could use the Better Finder Attributes utility.

A number of people have expressed the desire that LR make file Date Created match the photo metadata capture date.  You could add your me-too vote and detailed opinion to this feature request in the official Adobe feedback forum: Lightroom: Changes creation date of image files | Photoshop Family Customer Community . However, based on what Adobe product developers have said in the past and how the photo industry in general handles the issue, in my opinion it's unlikely Adobe will ever change the behavior of LR.