Substitutions are placeholders which can be used in the backup definition configuration.
📄️ File dates
For normal file systems different attributes like `mtime, ctime and atime exists to record the times of changes to files. Those values might change if and when files are copied to other locations like remote filesystems or object storages.
Purging is the process of deleting superfluous or outdated backups. By default, purging is disabled. You have to explicitly define a purge policy.