Dear Uillino,

Yes its possible. Try below code

Step 1: Import this library.

from datetime import datetime

Updated Answer with input case:

Step 2: Define the field in python file.

'dob': fields.date('Date Of Birth'),

Step 3: Write the onchange method

def dob_changed(self,cr,uid,ids,dob,context=None):

    if context is None:

    context = {}

    if dob: # datestring = "2015-08-10" 

        date = datetime.strptime(dob, '%Y-%m-%d')

        year = date.year

        month = date.month

        print 'year and month', year, month

Step 4: Define the field in XML file.

<field name="dob" on_change="dob_changed(dob)"/>

Hope this may help you :) 

Thanks & Regards

Ankit H Gandhi

check this link, it does not contain an answer to your question, but it may guide you.

Also https://www.odoo.com/apps/modules/6.0/web_mask_widget/, I didn't try it, but I think it would be helpful

Another related link is this one