Effect on Daylight Savings on attributes of backup files

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Bob S

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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.
 
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" 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.
 
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" 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.
 
Bob S 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
 
John Wunderlich 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.
 
"LD55ZRA" 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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