Produce a date for every month from start until end in Odoo

get_first_date_of_every_month.py

from datetime import datetime, timedelta, date

class some_model(models.Model):    
    _name = 'some.model'
    
    # creating date field in odoo class
    date_start = fields.Date(string="Start Date")
    date_end = fields.Date(string="End Date")
    
    @api.multi
    def calc_first_date_of_month(self,from_date, end_date, day=1):
        """Produce a date for every month from start until end"""
        start = from_date.year * 12 + (from_date.month - 1)
        end = end_date.year * 12 + (end_date.month - 1)
        if end_date.day > day:
            # end date is past the reference day, include the reference
            # date in the output
            end += 1
        # generate the months, just a range from start to end
        for ordinal in range(start, end):
            yield date(ordinal // 12, (ordinal % 12) + 1, day)
    
    @api.one
    def button_click(self):
        # converting string date value into python date object
        date_start = datetime.strptime(self.date_start, '%Y-%m-%d').date()
        date_end = datetime.strptime(self.date_end, '%Y-%m-%d').date()
        list_of_date = list(self.calc_first_date_of_month(date_start, date_end))
        print('***',list_of_date)

For Detail and Code Description: https://learnopenerp.blogspot.com/2021/07/how-to-use-and-convert-date-field-format-odoo.html