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Hierarchical File System Plus (HFS+), also known as Mac OS Extended, is a journaling file system that was developed by Apple as an update to its aging Hierarchical File System (HFS). It was introduced with Mac OS 8.1 in 1998 and remained in use until it was deprecated with the release of the Apple File System (APFS) with macOS 10.13 (Catalina) in 2017.


HFS Plus replaced the 16-bit block addresses of HFS with 32-bit addresses, allowing for drive sizes up to 8 exabytes. The previous file name limit of 31 characters was extended to 255 characters, though the Finder was not updated to take advantage of it until Mac OS X. However, it carried over the 2040 date limit from HFS, which was not remedied until the release of APFS.


In November 2022, a Mac OS X 10.2.2 (Jaguar) update added journaling, a form of logging of disk activity, to HFS Plus to reduce the likelihood of data corruption on a drive following an unexpected power outage, restart, or disconnection.[1]

Date limitation[]

HFS Plus and the Date & Time control panel from Mac OS 9.0.4 and later can manage dates up to February 6, 2040 at 06:28:15, after which the clock defined by its epoch will cycle back to January 1904.[2][3] To avoid this 2040 date limit, Apple has been migrating modern macOS users to its newer APFS file system since 2017.[4]


  1. Mac OS X 10.2.2 Gains Journaling by Matthew Rothenberg, eWeek. 2002-11-12.
  2. Why Do Older Macs Reset to 1904? by Jeff Adkins, Low End Mac. 2004-01-15.
  3. Solving Mac OS 8’s Y2K20 Bug by Josh Centers, TidBITS. 2020-01-03.
  4. Decoding the APFS file system by Kurt H. Hansen and Fergus Toolan, Norwegian Police University College. 2017-04-22. Revised 2017-06-21.

External links[]

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