Gold Membership (calendar or from date basis)

Hi,
I almost reached 100 likes and so my first 10 points for the gold membership

I was wondering if the Gold Membership subscription was on:

- a calendar basis (from the first day of the month until the last day of the month)
- a day basis (from the day of subscription, let’s say today is the 21st if I subscribe today the membership would end on the 21st next month).

Thanks for your feedback.
G