The Solar holiday recurrence rule type is for holidays that are based on solar events.
In some cases these solar events are well-known events such as the seasons, the equinoxes, or the solstices.
Vernal Equinox, Japan
Some solar holidays are based on a specific solar longitude that is not a multiple of 90 degrees (corresponding to the seasons, solstices and equinoxes).
Tamil New Year, India
These holidays are calculated using the default solar data source of the parent holidays set (or a specific solar data source if the use set's default is unchecked).
Topic 176440, last updated on 16-Apr-2020