important caveat with Rsync on NT and dayligt savings time

Lachlan Cranswick l.m.d.cranswick at
Tue Oct 29 20:37:01 EST 2002

I think this "day light savings" time stamp issue also affects 
Win98 as well - at least on a Win98 PC I use.  
Rsync insists on updating all the files fully.  
Shouldn't it just be resetting the times on the files 
if the files are the same size - or am I missing 
something here?


>Your description is as confusing as the KB article (at least
>to me).  Part of the problem with the KB article is that it
>focuses on localtime displays rather than internals.
>.From what i can tell FAT stores timestamps in localtime.
>NTFS uses a GMT based timestamp.
>I can see one of two places where we get bit.  As a matter
>of curiosity i'd like to know which.
>1. When the FAT timestamps are converted to GMT it is done
>   based on the current TZ offset rather than the TZ offset
>   in effect when the timestamp was made.
>2. The NT equivalent of stat(2) is converting the NTFS
>   timestamps to localtime and then the cygwin libs convert
>   it back to GMT.
>It would appear that the problem could be avoided either by
>using NTFS or FAT filesystems.  Yes?   It certainly sounds
>filesystem dependant.
>I'd guess that the correct place to fix this is in the
>cygwin libs.  They could be tweaked to recognize the TZ
>calculation error of the NT libs.  There might need to be a
>test for filesystem type (if possible) or a switch to
>determine behavior otherwise what fixes some will break

Lachlan M. D. Cranswick

Collaborative Computational Project No 14 (CCP14)
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  Birkbeck University of London and Daresbury Synchrotron Laboratory 
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