I am trying to add months on a date but I am finding problems to make it.

I tried this:

<span t-set="d_delta" t-value="datetime.timedelta(months=1)"/>
<span t-set="d_dateorder" t-value="datetime.datetime.strptime(doc.date_order,'%Y-%m-%d %H:%M:%S')"/>
<span t-set="d_desdedia" t-value="d_dateorder + d_delta"/>
<span t-esc="d_desdedia.strftime('%d-%m-%Y')"/>

But doesnt work.... how can I make it?