A calendar month is the period of duration from the first date of one month to the last date of the same month, which can vary from 28 to 31 days in length.
For purposes of determining the number of withdrawal requests occurring in a given month, IBKR uses the date at which the client submits the withdrawal request and not the date at which the withdrawal was processed. Accordingly, a client who submits a withdrawal request on the first and last days of the same month will be assessed a fee for the second request even if that request is processed on the first day of the following month.