Calculate a PayPal Subscription Renewal Date

For monthly billing cycles, recurring payments are collected on the same day of the month. If the initial recurring payment falls on the 31st, PayPal eventually adjusts the billing cycle to the 1st of the month. If the initial recurring payment falls on the 29th or 30th, PayPal adjusts the billing cycle to the cycle to the 1st of March following that skipped February.

This is useful for displaying a "renewal date" on a user dashboard for monthly-renewed PayPal subscriptions.

From the PayPal Documentation: https://www.x.com/thread/48147

**How Subscriptions with Monthly Billing Cycles Work**

For monthly billing cycles, recurring payments are collected on the same day
of the month. If the initial recurring payment falls on the 31st, PayPal
eventually adjusts the billing cycle to the 1st of the month. If the initial
recurring payment falls on the 29th or 30th, PayPal adjusts the billing
cycle to the 1st of the month on the following February.

When Monthly Recurring Payments Are Due and Collected on the 31st
The subscription terms are:

$25.99 USD a month; the subscriber signs up on Thursday, July 31.

The subscriber is billed as follows:

  Thursday, July 31 = $25.99 USD
  Saturday, August 31 = $25.99 USD
  Wednesday, October 1= $25.99 USD
  Saturday, November 1= $25.99 USD
  and so on...

Notice that no recurring monthly payment was collected in September, but
recurring payments were collected roughly every 30 days.

When Monthly Recurring Payments Are Due and Collected on the 30th
The subscription terms are:

  $25.99 USD a month; the subscriber signs up on Tuesday, December 30.

The subscriber is billed as follows:

  Tuesday, December 30 = $25.99 USD
  Friday, January 30 = $25.99 USD
  Sunday, March 1= $25.99 USD
  Wednesday, April 1= $25.99USD
  and so on...

Notice that no recurring monthly payment was collected in February, but
recurring payments were collected roughly every 30 days.

https://cms.paypal.com/cms_content/US/en_US/files/developer/PP_WebsitePaymentsStandard_IntegrationGuide.pdf (PDF)

python setup.py install

from paypal_date import get_next_paypal_monthly_billing_date

today = datetime.datetime.now()

next_month = get_next_paypal_monthly_billing_date(today)