Suggested Addition to strftime

As there appears to be no way to prune backups in some modules (i.e., MariaDB/Mysql Database Server) I went looking to see if strftime could be used to tell if a day is odd or even.
I could not find anything.
Is there any simple way to add to strftime so that we can backup to say “/backup/db-0.sql.gz” for odd and “db-1.sql.gz” for even days of a month (or year)?

Side note: I already have backups of the databases from the Virtualmin backup side.
These are additional backups but do not feel I need 7 of them (the minimum I have been able to do based on Weekday names).
Realistically: It would be nice if they could be pruned. (find “/base-backup-path/general-backup-names-etc/” where older than number of days -delete)

Thanks for reading my craziness – Any thoughts (other than adding a find -delete pre or post backup, which may be a possible temporary answer)?