In astronomy, an octaeteris (Greek: ὀκταετηρίς, plural: octaeterides) is the period of eight solar years after which the moon phase occurs on the same day of the year plus one or two days.
This means, that if Venus is visible beside the Moon, after eight years the two will be again close together near the same date of the calendar.
The octaeteris, also known as oktaeteris, was noted by Cleostratus in ancient Greece as a 2 923+ 1 /2 day cycle.
The 8 year short lunisolar cycle was probably known to many ancient cultures.
The mathematical proportions of the octaeteris cycles were noted in Classic Vernal rock art in northeastern Utah by J.Q.