Hi,

I want to make local backups using rsync daemon.

I expect, that everything works fine when I edit the /etc/rsyncd.conf file and make 'systemctl enable+start/restart rsyncd'

But where those file differences are stored?

And how do I restore a file to a different version or specific date?

You cannot. Or rather, you can but you are using the wrong tool. The tool rsync does a sync or clone of an existing file, folder, or tree between locations. (Where locations can be on the same server, or different servers connected via some network connection over which rsh or ssh can be established.)

If you want a point-in-time restore you need a REAL backup tool. Something like bacula may be overkill, and is complicated (and somewhat difficult) to get set up properly. Check your repositories for packages that answer to the 'backup' search term. Burp or BackupPC should be available.

rsnapshot

Just a footnote, to give an example of what rsync is used for, the Debian scripts for mirroring the Debian mirror uses rsync. rsync has some features that are nice for backup, but it lacks many features that you really need for a local backup program, such as incremental backup. You might have a look at backup ninja. It's dubbed: powerful lotus blossom against data loss.

Hm. playing with words....
Rsync will generate the difference on the fly, it will not store anything (just the files you want to sync). From the other hand rsync will always make an incremental (differential?) backup, it will only sync the changed files (and if you are lucky it will sync only the changed/modified parts of the files). The main goal of rsyncs are: make an exact copy of the specified files and lower the required network traffic.
It is not able to restore any previous version (of any file/dir), however you can rsync a given fileset/directories into different folders (for example week by week) and the identical (non-modified) files will be hardlinked to earlier instances, so only the differences will be really added to the target folders.

Actually you can find a lot of different examples on rsync incremental backup, here is an overview: http://webgnuru.com/linux/rsync_incremental.php

Ok thank you for all this useful information.

So I will use another program for versioning backups

Not sure if you looked up rsnapshot, it is using rsync to create versioned backups. Isn't this what you want?