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Daylight Savings Time and Macintosh Extended Format

Daylight Savings Time and Macintosh Extended Format -- As portions of the United States sprang ahead to daylight savings time last Saturday, reports of creation and modification time problems on Macintosh Extended Format (HFS Plus) volumes began to surface. (Extended Format is an optional element of Mac OS 8.1.) A disk formatted in Extended Format stores file creation and modification times in Greenwich Mean Time. When you check or uncheck the Daylight Savings Time checkbox in the Date & Time control panel, your computer's offset from GMT changes correspondingly. On an Extended Format disk, this changes the apparent creation and modification times for files; dates may change as well. Some people won't notice, but others may have problems; in particular, backups may take longer or fill backup media because every file will appear to have been modified.

<http://til.info.apple.com/techinfo.nsf/artnum/ n24452>

Dantz, makers of the popular backup program Retrospect, recommend either using the situation as an opportunity to make a full backup or changing the time using the Current Time field in the Date & Time control panel instead of the Daylight Savings Time checkbox. Another fix comes in the form of HFS+ DST Timefix, a tiny extension from Glenn Austin that causes Extended Format to ignore the fact that the Daylight Savings Time checkbox is checked. For extensive information about Extended Format, see "All About Macintosh Extended Format (HFS Plus)" in TidBITS-414. [TJE]

<http://www.dantz.com/technical_support/ technotes/tn-405.html>


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