File dates come in two varieties:
dates that are part of the file system directory, e.g. file creation date, file modification date, file added date
dates that are embedded in the actual file, e.g. shooting dates, content created dates, media created dates, track created dates, etc.
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
HFS+ (Journaled), memory sticks as
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 A Better Finder Attributes all involve manipulating embedded 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.
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
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.
Spotlight Added Date is derived from an
extended attribute that is set by the Finder. The
Date is set by Safari and other download programs.