In Aragorn the King Elessar's New Reckoning calendar, 30 Yavannië was made a festival in honor of the Ring-bearer, since it corresponded with Frodo's birthday, 22 September in the Shire Calendar. Except in leap-years 30 Yavannië corresponded with 21 September in the Shire Calendar (due to its Overlithe leap-day at midsummer), so the New Reckoning's leap-day was inserted between Yavannië and its Enderi and Frodo's birthday feast was doubled in leap-years. It's not clear if the last day of the month of Yavannië was still referred to as "30 Yavannië", or if this day, and the leap-day, were simply called Cormarë.
 Uses outside the legendarium
22 September is a popular "ceremonial" date for founding Tolkien societies. Unquendor (the Netherlands), Eredain (Switzerland), Imladris (Denmark) and several others were founded on this day. Another ceremonial day is 3 January, the birthday of J.R.R. Tolkien.