Amazon's monthly rental is calculated based on the calendar month (that is, from the 1st to the last day of each month). If you join the rental plan in the middle of the month, your rental will start from the date of joining until the end of that month.

If you join the rental plan at the end of the month, your rental will start from the next month until the end of the next month.

If you want to end your subscription during the rental period, make sure to cancel it before the end of the month to avoid being deducted from the next month's rental. It is worth noting that due to the different time zones of each country and region, Amazon's monthly rental time will be calculated based on local time, so some users may have problems crossing the date line.