Ok I think I see what you mean.
The only time format that is needed is the year. We actually don't need more info than that.
For parameter formatting I am using setters in the parent class.
See:
https://github.com/geoadmin/mf-chsdi3/pull/212/files#diff-3da6caa6f57eb4bea37fecb83d07bfd6R138