Hi,

You can try this code for calculating the days

import datetime

def generate_invoice(subscription_start_date):
    # Calculate the next billing date (15th of the next month)
    next_billing_date = subscription_start_date.replace(day=15)
    if next_billing_date         next_billing_date += datetime.timedelta(days=30)

    # Calculate the due date (10 days after the billing date)
    due_date = next_billing_date + datetime.timedelta(days=10)

    # Generate the invoice
    invoice.write({
        "billing_date": next_billing_date,
        "due_date": due_date
        # Add other invoice details as needed
    })

Hope it helps