Base on my understanding, the rate date is refer to POSTING DATE.

Because transaction date is not necessarily the same as the settlement date, which can happen several days after the transaction occurs. Example, u swipe the credit card merchant and available credit will be reduced accordingly BUT the merchant is show pending transactions. Once merchant banks submit payment to credit card issuers bank, then it is POSTING DATE. Credit Card issuers Bank never count pending transaction caz merchant bank no submit payment to credit card issuers bank, So conclusion is POSTING DATE.

If i was wrong don shoot me