A lunisolar calendar is a calendar in many
cultures whose date indicates both the moon phase and the time of
the solar year. If the solar year is defined as a tropical year
then a lunisolar calendar will give an indication of the season; if
it is taken as a sidereal year then the calendar will predict the
constellation near which the full moon may occur. As with all
calendars which divide the year into months there is an additional
requirement that the year have a whole number of months. In this
case ordinary years consist of twelve months but every second or
third year is an embolismic year which adds a thirteenth
intercalary embolismic or leap month.