When I save a file it has a 'Created At' and 'Updated At' Value saved as well. I would like to know HOW these values are saved? Are they saved as an integer representing a number of seconds since 1904? or are they saved as some kind of string data? Also Where are they saved? as part of the file itself or in the desktop file?

1 Answer 1


The HFS filesystem stores file metadata in a single large file called the "catalog file", with one record for each file or directory. Creation and modification times are stored as 32-bit unsigned integers representing a count of seconds since midnight, January 1, 1904.

(Source: Inside Macintosh: Files)

  • 3
    This is not just a retrocomputing issue, current HFS+ volumes have a timestamp resolution of 1 second because of compatibility with HFS APIs. In fact MacOS X is upwards compatible with most of the metadata from Classic MacOS like labels and icon positions. Commented Dec 1, 2016 at 15:46
  • 3
    One of the reasons apple is working on a new filesystem for the next version of OS X Commented Dec 1, 2016 at 16:58
  • I find the choice of epoch rather curious given that languages such as Pascal had a 32-bit signed type but no 32-bit unsigned type, and as a consequence any time after the formation of Apple Computer would have been stored as the number of seconds "since" February 6, 2040, at 6:28:16am.
    – supercat
    Commented Oct 3, 2022 at 19:27

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