The public holidays in Spain have been published in the Boletín Oficial del Estado for 2017.
There are 9 dates the same throughout Spain including:
6 January - Epifanía del Señor / Día de Reyes
14 April - Viernes Santo
1 May - Fiesta del Trabajo
15 August - Asunción de la Virgen
12 October - Fiesta Nacional de España
1 November - Todod Santos
6 December - Día de la Constitución
8 December - Inmaculada Concepción
25 December Natividad del Señor / Navidad
Next year, three of the fiesta dates fall on a Friday including 6 Jan, 14 Apr and 8 Dec plus two fall on a Monday including 1 May & 25 Dec, allowing for a long bank holiday weekend.
In the Canary Islands the 30 May is an additional fiesta day for the Día de Canarias.
We’ll add the municipal fiestas for Lanzarote once they have been confirmed.