The Elven Calendar is a twelve month, thirty day calendar based on the lunar cycle of Potos. This calendar is imperfect, and over the years the seasons have drifted from one month to the next. Recently, the end months have become summer months, but as recently as two thousand years ago the summer was recorded in the eighth and ninth months. Many attempts have been made to adjust the calendar, but none really stuck, and over the generations people have just become accustomed to the drifting seasons. It’s part of the calendar’s charm, so to speak.
Each month has an elven name, but over the centuries they have fallen into disuse. It is much more common to just say “Third Month,” “Fifth Month,” etc, when indicating months.