in Ireland are aligned with the sunrise around the times of Imbolc and Samhain. This includes the Mound of the Hostages on the Hill of Tara, and Cairn L at Slieve na Calliagh. Frank Prendergast argues that this alignment is so rare that it is a product of chance.

Hutton writes that Imbolc must have been "important enough for its date to be dedicated subsequently to Brigid