The Interfaith Network for the UK calendar of religious festivals harnesses the information on religious festivals from and with permission of the Shap Working Party on World Religions in Education, and is used here with permission (Shap and its calendars are also featured in this resource here).  The Shap calendar of religious festivals was a first of its kind, and is produced in consultation with religious organizations each year.

Calendar of Religious Festivals – Interfaith Network for the UK