Credit card expiration dates - Inclusive or exclusive?

It took me a couple of minutes to find a site that I could source for this.

The card is valid until the last day of the month indicated, after the last [sic]¹ day of the next month; the card cannot be used to make a purchase if the merchant attempts to obtain an authorization. - Source

Also, while looking this up, I found an interesting article on Microsoft's website using an example like this, exec summary: Access 2000 for a month/year defaults to the first day of the month, here's how to override that to calculate the end of the month like you'd want for a credit card.

Additionally, this page has everything you ever wanted to know about credit cards.

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1. This is assumed to be a typo and that it should read "..., after the first day of the next month; ..."

If you are writing a site which takes credit card numbers for payment:

1. You should probably be as permissive as possible, so that if it does expire, you allow the credit card company to catch it. So, allow it until the last second of the last day of the month.
2. Don't write your own credit card processing code. If^H^HWhen you write a bug, someone will lose real money. We all make mistakes, just don't make decisions that turn your mistakes into catastrophes.