how to preserve file modification time with LFTP

On the following page

http://www.bouthors.fr/wiki/doku.php?id=en:linux:synchro_lftp

the authors state:

When uploading, it is not possible to set the date/time on the files uploaded, that's why –>ignore-time is needed.

so if you use the flag combination --only-newer and --ignore-time you can achieve decent backup properties, in such a way that all files that differ in size are replaced. Of course it doesn't help if you really need to rely on time-synchronization but if it is just to perform a regular backup of data, it'll do the job.