bug#11798: touch date bug

[Bob Proulx]

Eric Blake wrote:
> Patrick Castet wrote:
> > $ touch a0.a
> > $ touch -d "20000102 03:04:05" a0.a
> > if you check with widows  cmd, you get 
> > a0.a is dated with  20000102 04:04
> > 
> > wich is not correct !
> 
> Welcome to the joys of Microsoft's decision to store file timestamps
> with respect to local timezones rather than with respect to UTC, even
> though that means that physically relocating your machine to a spot with
> different daylight savings rules renders those timestamps ambiguous.
> The difference of one hour that you are seeing is due to Windows'
> insistence on applying a (possibly wrong) daylight savings adjustment,
> based on the timestamp on the file vs. what Windows considers as your
> current time zone.

Additionally it appears you are operating on a FAT filesystem.  MS FAT
filesystems represents times with only a 2-second resolution.  This
causes all timestamps to be even second values.  Odd second values are
modified to fit.  This is the :05 time being set to :04 that is
illustrated above.

This problem for example caused 'rsync' to include a --modify-window
option so that it can be used like --modify-window=1 to allow times to
differ by up to 1 second to work around this issue.

Bob