[syslog-ng]Rotate my logs files

[Moktar KONE]

Hi ,
I am testing syslog-ng and I want to know how can I rotate my logs file .
To logs messages I have a directory for many hosts, for each host, logs are
classified by facilities, I  have a new log file each day for each facility.
so the name of my logs files changes according to the date.
how can rotate the old log files? the logs of 2days ago? 3days ago?
thanks
this is the section that logs my files :
  destination hosts {

  file("/var/log/HOSTS/$HOST/$FACILITY/$FACILITY_$YEAR_$MONTH_$DAY"
    create_dirs(yes));
};