Synchronize two folders in both way; criteria: last changed

[Dvorzhetsky <dvorzhetsky@airpost.net>]

Hello,

First I'll explain the situation: I have an archive folder with images, 
text and other type of files. I used to backup this folder from time to 
time but at some point I stop doing that and got confuse (or messy:) and 
start to edit files in the backup and/or to add files to the 'current' 
folder.

I'd like to rationalized that by synchronizing the backup and current in 
both way:

- keeping only the version of the files which have been the most 
recently changed.
- if a file or a subfolder is present in one folder and not the other 
I'd like to always keep it.

I look into mann rsync but I'm always asked to choose one source and one 
destination, which is obviously not what I want to do. Is there a way to 
do that with rsync? How?

Maybe with another software?

can someone give a hand?
Cheers!