Which connector are you using to get the datasets?
I think what Max is saying is that if you’re querying the datasets via SQL you should be able to use date_trunc(‘month’,updated_date) in one dataset and date_trunc(‘month’,cm_actual_departure_dt) in the other to get the month then join on these.
This means you will have one common x axis in the final dataset, which should allow you to combine both values in one visual.
Depending on your sql technology here is something you can do.
SELECT date_trunc(‘month’,updated_Date) month, legal_po_id, ad_po FROM table po_changed
LEFT JOIN (SELECT date_trunc(‘month’,cm_actutal_departure_dt_554) month, ad_po FROM table) shipped_po ON po_changed.month=shipped_po.month