File Date Primer

File dates come in two varieties:

1. dates that are part of the file system directory, e.g. file creation date, file modification date, file added date

2. dates that are embedded in the actual file, e.g. shooting dates, content created dates, media created dates, track created dates, etc.

For the long version, including Date Added and Last Opened and which of these dates the Finder, Spotlight, Apple Photos and Final Cut Pro each read, see the public guide Which date does your Mac actually use?.

Your hard disk, SSD, network drive, USB stick & SD Card all use a native “file system”. Your Mac’s main drive will usually be formatted either as APFS or HFS+ (Journaled), memory sticks as FAT32, exFAT or NTFS.

All file systems keep a central catalog that contains information about each file’s location on the disk, its name and when the file was first created and last modified. These are the values that are described as file creation date, file modification date.

Modern file systems also often feature “extended file attributes”, which are kept as separate files and give details about the file itself.

A second and more important kind of file date are “embedded dates”, which are stored in the file’s “meta-data” and are part of the file itself. As it is part of the file itself, the meta-data will always be copied along with the file and will never change unless you edit the file content. When you do edit the file, it is up to the application that you use to correctly save all the meta-data again. Many applications do not. Many applications discard the entire meta-data when you save a file after editing. Some applications know about some of the meta-data but not all of it. Some applications deliberately change the meta-data to reflect the editing that was performed.

Therefore you should always keep a backup of your original image & movie files, so that you don’t risk losing precious meta-data.

The most common use cases for File Multi Tool all involve the embedded dates:

• to make images & movies sort correctly in the Finder (copy the shooting date to the file creation date)
• to ensure that images & movies sort properly in Apple’s Photos and other image management applications
• to correct incorrectly set camera clocks and time zones (adjust the dates)

Finally, a word about “Spotlight” metadata and the related dates: Spotlight Content Creation Date, Spotlight Content Modification Date, Spotlight Download Date, Spotlight Added Date.

Spotlight is Apple’s technology for quickly searching for files & other data using names, meta-data and content. It works by looking up search terms in its database. That database is created by running Spotlight importers on source files. Each importer knows how to extract data from a particular file type and store this information in Spotlight’s database. Furthermore, the Spotlight database also contains some information that is put there by Safari, the Finder, etc.

The Spotlight Content Creation Dates & Spotlight Content Modification Dates are derived from the embedded meta-data of the particular file type using the importer for that format. So, for JPEG format files, they will be derived from the DateTimeOriginal and/or DateTimeDigitized timestamps. You cannot directly manipulate these fields. Instead you need to change the underlying embedded dates and Spotlight will notice this and refresh its database.

The Spotlight Added Date is derived from an extended attribute that is set by the Finder. The Spotlight Download Date is set by Safari and other download programs.