Description:

ls4sweep should be used as helper for removing extra old daily-created backups.

Sweeping policy consists from the set of records, where each record contains
the count of intervals (or periods) and the length of one period (in days).
ls4sweep checks creation or modification time of given files and displays names
of those when they mismatch policy. Only one file is keeping in each interval.

Consider following command:
ls4sweep 3:1,2:3,2:10,2:30,3:90,5:365 *.zip
This means:
- keep daily ZIP-archives in current directory for last 3 days
- older than 3 days - keep 2 archives with 3-days delta
- older than 9 days (3*1 + 2*3) - 2 archives with 10-days delta
- older than one month (3*1 + 2*3 + 2+10) - 2 archives with monthly delta
- older than 3 months - 3 archives with 90-days delta
- older than one year - yearly archive for five years
- display filenames of all remaining stuff

ls4sweep output can be directly passed to '| xargs -r /bin/rm -f' command.
When you create archives via cron(8), you can put cleanup via ls4sweep call
after creation.