The two moons of Orr. The months are established based on their orbits.
Adele is the smaller of the moons and has a shorter orbit, lasting only approximately 28 1/2 days.
Lilith is the larger and has an orbit of approximately 61 1/2 days.
Traditionally, the day after Lilith's orbit is the end of the month, which is new moon to new moon. When Lilith is a new moon, it has been considered a non-day, though that has not been observed by humans or Yeti for several hundred years.
The Vibranni also have a calendar based on the moons. Unlike human and Yeti calendars which follow Lilith, the Vibranni count from the orbit of Adele. Every 4.8 years, both moons exist full in the sky. This is celebrated as the New Year by the Pavostanni, Pocanni, and Detstanni.