Hi,
in "Duplicate Mode" all target files will get the date of synchization as time stamp. This way all information is lost about individual file creation dates. Target files should have the same dates as their corresponing source files.
This problem becomes obvious when starting "Duplicate Mode" a second time. All files will be copied again from source to target since they have differnt dates.
FTP Synchronization - time stamps
Unfortunately this is limitation of FTP protocol - there is no way to set file time on server - and server always set uploaded file time to current time. To handle this problem currently we offer option to create listing file on server, next update will also add an option to set local files times equal to remote files, this will also help.