Lunisolar holidays are based on lunar events that either occur after a given solar event has occurred, or whose exact date depends on the time of Sunrise or another time of the day based on the Sun's trajectory.

Navam Full Moon Poya Day, Sri Lanka
In all cases, the holiday is calculated using either a specific Lunar Data Source or the default Lunar Data Source of the parent holidays set.
See also: Solar Holidays Rules and Recurrence Rules Options.