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:
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!
For a
comprehensive discussion about this issue refer
to:
http://www.codeproject.com/KB/datetime/dstbugs.aspx
Solution:
In order to avoid re-copying files that have a modification time difference of +-1h FreeFileSync offers a global option: Menu -> Advanced -> Global settings: Ignore 1-hour file time difference.
If "Ignore 1-hour file time difference" 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 .
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).
Note:
If synchronization
takes place between NTFS ↔ NTFS or FAT32 ↔ FAT32 this
checkbox provides no advantage and can be left unchecked.