The clock starts ticking as soon as your application is approved, not some time later when your card arrives in the mail. So it means you need to start spending as soon as you receive the card if you're going to meet the target (unless you have a major purchase in mind). And since some card issuers advise the time limit in days (e.g. within 90 days of card approval) while other do it in months (e.g. within two months of card approval) it's best to assume that each month has only 30 days and get your spending done in 60 or 90 days, depending on the requirement.