How do I calculate the next renewal date for my subscription?
I have set up a subscription plan that will automatically charge users every month, every three months, and every year. The problem is, how can I calculate the exact date for charging the user? Can't we charge every 30 days? Because not all months have 30 days. If we charge on a purchased date, people who bought the plan on January 30th won't be billed in February because there aren't 30 in February. This is a bit of a tricky issue. How can I solve this?
PS: I'm using ruby on the rails
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You can save the date subscribed_on
and number_of_payments
user already made. Then calculate the next payment date by incrementing number_of_months
and using the >>
date method . >>
takes into account the number of days per month:
# at subscription date and first payment
subscribed_on = Date.today # in the example: 2015-01-30
number_of_payments = 1
next_payment_date = subscribed_on >> number_of_payments
#=> 2015-02-28
# after next payment (on 2015-02-28)
number_of_payments = number_of_payments + 1
next_payment_date = subscribed_on >> number_of_payments
#=> 2015-03-30
# after next payment (on 2015-03-30)
number_of_payments = number_of_payments + 1
next_payment_date = subscribed_on >> number_of_payments
#=> 2015-04-30
From the documentation
d >> n
→date
Returns a date object indicating n months after itself. The n value must be numeric.
This leads not only to the correct dates, but also to optimized queries for next_payment_date
, and statistics - the average length of the subscription period per month.
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