When backing up to S3 storage, the operator creates folder names such as

prod-2020-11-06-00:00:04-full

This example was actually created on 11th June, so the date format is YYYY-DD-MM which is very unconventional!

I believe this is the relevant line: 

https://github.com/percona/percona-xtradb-cluster-operator/blob/c6c4b7a127ed83a905c5c180b42bc7532694a940/pkg/controller/pxcbackup/controller.go#L177