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<H2 CLASS="western" STYLE="font-style: normal"><FONT FACE="Tahoma, sans-serif">Daylight
saving time</FONT></H2>
<P STYLE="margin-bottom: 0cm"><BR>
</P>
<P STYLE="margin-bottom: 0cm"><FONT FACE="Tahoma, sans-serif">The
Windows operating system exhibits quite a unique behavior when
handling timestamps on NTFS file systems. This leads to a well-known
issue that all file synchronization software has to handle:</FONT></P>
<P STYLE="margin-bottom: 0cm"><FONT FACE="Tahoma, sans-serif">During
daylight saving time switching, (local) file times are shifted by one
hour on NTFS file systems, while NO shift occurs on FAT/FAT32 drives
(as used by most USB sticks)! Thus when synchronizing an NTFS against
a FAT32 volume file times become asynchronous twice a year!</FONT></P>
<P STYLE="margin-bottom: 0cm"><FONT FACE="Tahoma, sans-serif">For a
comprehensive discussion about this issue refer
to:<BR><A HREF="http://www.codeproject.com/KB/datetime/dstbugs.aspx">http://www.codeproject.com/KB/datetime/dstbugs.aspx</A></FONT></P>
<P STYLE="margin-bottom: 0cm"><BR>
</P>
<P STYLE="margin-bottom: 0cm"><FONT FACE="Tahoma, sans-serif"><B>Solution:</B></FONT></P>
<P STYLE="margin-bottom: 0cm"><FONT FACE="Tahoma, sans-serif">In
order to avoid re-copying files that have a modification time
difference of +-1h FreeFileSync offers a global option: <I>Menu ->
Advanced -> Global settings: Ignore 1-hour file time difference</I>.</FONT></P>
<P STYLE="margin-bottom: 0cm"><FONT FACE="Tahoma, sans-serif">If
"<I>Ignore 1-hour file time difference</I>" is checked, all
files with a +-1h difference are treated as having the same time.
This also handles different file time precisions (NTFS: 100ns,
FAT/FAT32: 2 seconds) by allowing a 2 second tolerance .</FONT></P>
<P STYLE="margin-bottom: 0cm"><FONT FACE="Tahoma, sans-serif">Files
that have a deviation of less than one hour are categorized as
conflicts. The reasoning is that these files surely have been
modified on at least one side since last synchronization. But during
one of the two daylight saving time switches per year the older file
is shown pretending a newer date which can lead to data loss (when
using the rule to overwrite older with newer files).</FONT></P>
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<FONT FACE="Tahoma, sans-serif"><B>Note:</B><BR>If synchronization
takes place between NTFS ↔ NTFS or FAT32 ↔ FAT32 this
checkbox provides no advantage and can be left unchecked.</FONT></P>
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