It can be really useful when planning a visit anywhere to be aware of any national, regional or local holidays, planning a day around visiting somewhere and then finding it shut is not much fun!
Cantabrian public holidays are the following days:
1 & 6 January, Maunday Thursday and Good Friday (not Easter Monday), 1 May, 15 August, 15 September (Día de Cantabria), 12 October, 1 November, 6, 8 & 25 December.
The Cantabrian school year calendar might also be useful to know when Cantabrian school holidays are. These are not always the same as elsewhere in Spain.
As you’ll see from the school calendar, the custom in Spain with any public holidays which fall on a Tuesday or Thursday, the Monday or Friday are sometimes also taken off too to form a puente, a bank holiday weekend. These times are particularly busy, and are often considered by the hospitality industry as peak periods, and therefore have high season prices.
It’s also useful to know when each individual town’s fiesta days are, as you’re also likely to find a least the shops and possibly roads shut there on those days, and usually also some kind of celebration going on, which might also be of interest.