BUG: File timestamps written under Linux to a VFAT file system are incorrect under MS-DOS when the Linux Local Time is determined by a "dual" timezone variable, e.g., TZ=EST5EDT, representing Standard/Daylight time. OBSERVED WITH: Red Hat Linux v6.0 (Intel), kernel version 2.2.5-15; MS-DOS versions 6.22 and 7 (Windows 98). DETAILS: Timestamps for files on an ext2 file system are maintained as UTC whereas for files on a VFAT file system they are by design maintained as Local Time. When the computer's Local Time is determined by a "single" timezone variable, e.g., TZ=EST5, files are written to a VFAT file system with the correct Local Time insofar as both Linux and MS-DOS are concerned. When however the computer's local time is determined by a "dual" timezone variable, e.g., TZ=EST5EDT, the time offset used is _always_ that of the Daylight part of the variable, e.g., "EDT", regardless of the system date or file date. Thus when a file originally created in Standard time is examined under MS-DOS (or with the mtools utility 'mdir') the Local Time is off by one hour. (Note: The Local Time as displayed under Linux is correct.) The same problem is observed on all VFAT media: Hard drive, Floppy disk, Iomega ZIP disk. EXAMPLE: Consider two files created on an ext2 file system, both at 07:00 UTC, but one in January and the other in July. A directory listing under Linux with Local Time determined by TZ=EST5EDT displays the file times as: Jan.txt 02:00 Jul.txt 03:00 exhibiting the correct 5 and 4 hour offsets from UTC for Standard and Daylight times. If both files are now copied to a VFAT file system, say on a floppy disk, while preserving the file dates ('cp -p'), Linux still displays the same Local Times as above. But if the floppy directory is displayed under MS-DOS (or with the mtools utility 'mdir'), the file times are both 03:00. (Note: An examination of the file time bit-fields in the floppy directory also shows them to be both 03:00). ADDITIONAL INFO: The same problem exists regardless of: system date; whether the hardware clock is maintained in UTC or Local Time; whether the /etc/localtime link is set to .../US/Eastern or .../UTC (the last with TZ=EST5EDT).