Monthly group

[menomalee]

In the documentation there is:

duration | string | 1h | v1.0.0 | If func is not raw only. It builds buckets of states over a duration. Doesn't work for months. Eg of valid values: 2h, 1d, 10s, 25min, 1h30, ...

Is this something that can be implemented? Or there's a reason behind 1 month is not a possible value?
This can be helpful of course in yearly graphs.

Thanks