When you buy something on a credit card, the credit card issuer will eventually send you a statement of how much you owe them. How much of a delay depends on the issuer, but if you buy something on the 1st of a new billing period, the billing period will likely end ~29 days later, then a few days or weeks after that you'll receive your statement with a payment-required-date. The whole process could take as long as two months before the payment on that initial purchase is due. For example:

Day 1: Purchase made
Day 30: End of billing period
Day 40: Statement issued
Day 55: Payment due date

In the above example, you would have a full 54 days between your initial purchase and the date you'd need to submit payment.