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Effect on Daylight Savings on attributes of backup files

Discussion in 'Windows XP' started by Bob S, Mar 14, 2010.

  1. Bob S

    Bob S Flightless Bird

    I use a portable drive to keep files synchronized between my
    home and office computers.

    The problem is that when Daylight Savings Time arrives the
    files on the portable drive get out of sync with the desktop
    computers by one hour. This doesn't necessarily cause a
    problem with my synchronization program, because the time
    difference apparently doesn't change the files' CRC numbers
    (if that's what they're called). I wouldn't have expected
    that, but it apparently seems to be so.

    Still, once Daylight Savings Time strikes, in the file
    attributes the creation and modification dates of *all* of
    the files on the portable drive become one hour "older" than
    the ones on the desktops. In the fall, when Standard Time
    comes back, the converse happens.

    Because there are so many files (well over 100,000), were I
    to synchronize them by time of modification rather than by
    CRC, it would take forever to get them back in sync. Also,
    I'm concerned that some day this "de-synchronizing" of the
    file times could cause confusion leading to a mistake on my
    part if the time of creation or modification of a file ever
    became important for some reason.

    I'd appreciate any suggestions on how to keep the times
    coordinated on these files. Leaving the portable drive
    connected to a desktop overnight doesn't do it.

    Thanks.

    --

    Bob S.
     
  2. LD55ZRA

    LD55ZRA Flightless Bird

    You should switch off your computer for one hour between 1:00:00 and 2:00:00
    or between 2:00:00 and 1:00:00 depending on whether the clocks are going
    forward or backward. The system is smart enough to deal with these things.

    In actual fact the switching off is only required for one minute before the
    hour and one minute after the hour. So two minutes in total. I would have
    thought most people's systems are logged off during this critical time on
    our planet! Or clocks (In United Kingdom) don't go forward until 28th March
    2010. Normally last Sunday in March.

    hth

    "Bob S" <BobS@xoxoxxx.com> wrote in message
    news:9s9qp55rm45hvqpno8ir78th3tuekculj5@4ax.com...
    >I use a portable drive to keep files synchronized between my
    > home and office computers.
    >
    > The problem is that when Daylight Savings Time arrives the
    > files on the portable drive get out of sync with the desktop
    > computers by one hour. This doesn't necessarily cause a
    > problem with my synchronization program, because the time
    > difference apparently doesn't change the files' CRC numbers
    > (if that's what they're called). I wouldn't have expected
    > that, but it apparently seems to be so.
    >
    > Still, once Daylight Savings Time strikes, in the file
    > attributes the creation and modification dates of *all* of
    > the files on the portable drive become one hour "older" than
    > the ones on the desktops. In the fall, when Standard Time
    > comes back, the converse happens.
    >
    > Because there are so many files (well over 100,000), were I
    > to synchronize them by time of modification rather than by
    > CRC, it would take forever to get them back in sync. Also,
    > I'm concerned that some day this "de-synchronizing" of the
    > file times could cause confusion leading to a mistake on my
    > part if the time of creation or modification of a file ever
    > became important for some reason.
    >
    > I'd appreciate any suggestions on how to keep the times
    > coordinated on these files. Leaving the portable drive
    > connected to a desktop overnight doesn't do it.
    >
    > Thanks.
    >
    > --
    >
    > Bob S.
     
  3. Big_Al

    Big_Al Flightless Bird

    LD55ZRA said this on 3/14/2010 4:02 PM:
    > You should switch off your computer for one hour between 1:00:00 and 2:00:00
    > or between 2:00:00 and 1:00:00 depending on whether the clocks are going
    > forward or backward. The system is smart enough to deal with these things.
    >
    > In actual fact the switching off is only required for one minute before the
    > hour and one minute after the hour. So two minutes in total. I would have
    > thought most people's systems are logged off during this critical time on
    > our planet! Or clocks (In United Kingdom) don't go forward until 28th March
    > 2010. Normally last Sunday in March.
    >
    > hth
    >
    > "Bob S"<BobS@xoxoxxx.com> wrote in message
    > news:9s9qp55rm45hvqpno8ir78th3tuekculj5@4ax.com...
    >> I use a portable drive to keep files synchronized between my
    >> home and office computers.
    >>
    >> The problem is that when Daylight Savings Time arrives the
    >> files on the portable drive get out of sync with the desktop
    >> computers by one hour. This doesn't necessarily cause a
    >> problem with my synchronization program, because the time
    >> difference apparently doesn't change the files' CRC numbers
    >> (if that's what they're called). I wouldn't have expected
    >> that, but it apparently seems to be so.
    >>
    >> Still, once Daylight Savings Time strikes, in the file
    >> attributes the creation and modification dates of *all* of
    >> the files on the portable drive become one hour "older" than
    >> the ones on the desktops. In the fall, when Standard Time
    >> comes back, the converse happens.
    >>
    >> Because there are so many files (well over 100,000), were I
    >> to synchronize them by time of modification rather than by
    >> CRC, it would take forever to get them back in sync. Also,
    >> I'm concerned that some day this "de-synchronizing" of the
    >> file times could cause confusion leading to a mistake on my
    >> part if the time of creation or modification of a file ever
    >> became important for some reason.
    >>
    >> I'd appreciate any suggestions on how to keep the times
    >> coordinated on these files. Leaving the portable drive
    >> connected to a desktop overnight doesn't do it.
    >>
    >> Thanks.
    >>
    >> --
    >>
    >> Bob S.

    >
    >

    My PC was in hibernate all night and this happened to me too today.
    Wouldn't your logic apply there or should you do a real power down?

    Granted my list of files is smaller and I have the backup never to copy
    "older" files, so some updated from before last time change were still
    there and thus the same hour, it only updated the recent changes in 6mos
    or so. I suspect for me that will never happen again now that I've
    done the update 2 times in a row now with "older" skipped.
     
  4. John Wunderlich

    John Wunderlich Flightless Bird

    Bob S <BobS@xoxoxxx.com> wrote in
    news:9s9qp55rm45hvqpno8ir78th3tuekculj5@4ax.com:

    > I use a portable drive to keep files synchronized between my
    > home and office computers.
    >
    > The problem is that when Daylight Savings Time arrives the
    > files on the portable drive get out of sync with the desktop
    > computers by one hour. This doesn't necessarily cause a
    > problem with my synchronization program, because the time
    > difference apparently doesn't change the files' CRC numbers
    > (if that's what they're called). I wouldn't have expected
    > that, but it apparently seems to be so.
    >
    > Still, once Daylight Savings Time strikes, in the file
    > attributes the creation and modification dates of *all* of
    > the files on the portable drive become one hour "older" than
    > the ones on the desktops. In the fall, when Standard Time
    > comes back, the converse happens.
    >
    > Because there are so many files (well over 100,000), were I
    > to synchronize them by time of modification rather than by
    > CRC, it would take forever to get them back in sync. Also,
    > I'm concerned that some day this "de-synchronizing" of the
    > file times could cause confusion leading to a mistake on my
    > part if the time of creation or modification of a file ever
    > became important for some reason.
    >
    > I'd appreciate any suggestions on how to keep the times
    > coordinated on these files. Leaving the portable drive
    > connected to a desktop overnight doesn't do it.


    This pops up every year about this time.

    This is caused by the disk file systems involved. NTFS file systems
    (typically used by Windows XP and newer) save file date/time as an
    absolute time in UTC (GMT) format. FAT and FAT32 file systems
    (likely to be what your external drive is) stores dates/times in
    "local time". This can cause a 1 hour discrepancy when Daylight
    Savings time comes into/out of effect or when moving a computer
    between time zones.

    To correct this permanently, format your external drive as NTFS
    (backup your data first).

    HTH,
    John
     
  5. Bob S

    Bob S Flightless Bird

    John Wunderlich <jwunderlich@lycos.com> wrote:

    > To correct this permanently, format your external drive as NTFS
    > (backup your data first).


    I'll do that.

    Thanks for the advice.
    --

    Bob S.
     
  6. Bob S

    Bob S Flightless Bird

    "LD55ZRA" <LD55ZRA@discussions.microsoft.com> wrote:

    > You should switch off your computer for one hour between 1:00:00 and 2:00:00
    > or between 2:00:00 and 1:00:00 depending on whether the clocks are going
    > forward or backward. The system is smart enough to deal with these things.
    >
    > In actual fact the switching off is only required for one minute before the
    > hour and one minute after the hour. So two minutes in total. I would have
    > thought most people's systems are logged off during this critical time on
    > our planet! Or clocks (In United Kingdom) don't go forward until 28th March
    > 2010. Normally last Sunday in March.


    My memory may be a bit feeble, but I have the impression
    that in the past I've had the computer shut down when the
    time change occurred, but I still had the problem with files
    being out of sync. Not sure though. In any case, I'll follow
    John's advice about formatting the drive as NTFS.

    Thanks for the response.
    --

    Bob S.
     

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