There is no specific web-hook to notify you that any particular credit-card is expiring some days later. So you need to keep the payment source details in your local system and keep asking if any is expiring after X days.
Credit card expiration dates printed on cards usually consist of a month and year only. In such cases, the cards remain valid until the last calendar day of that month. If, for example, an expiration date reads 06/15, this means it can be used until midnight on June 30, 2015. If you attempt to use the card after this time, it will be declined.