Giezel,

Module swr_datepicker can be used for  v10.  but you are using v9.

See the alternative solution

Py

# Outside the model
def get_years():
    year_list = []
    for i in range(2016, 2036):
        year_list.append((i, str(i)))
    return year_list

# Inside the model
month = fields.Selection([(1, 'January'), (2, 'February'), (3, 'March'), (4, 'April'),
                          (5, 'May'), (6, 'June'), (7, 'July'), (8, 'August'), 
                          (9, 'September'), (10, 'October'), (11, 'November'), (12, 'December'), ], 
                          string='Month',
year = fields.Selection(get_years(), string='Year',)

xml

<group> 
    <div>
        <label for="month" string="Month"
               style="font-weight: bold !important;margin-right:107px;margin-left: 0px;"/> 
        <field name="month" style="width:110px"/>
        <field name="year" style="width:110px;margin-left: 34px;"/>
    </div>  
</group>

All the best !