When is Spain's National Day celebrated?
This holiday is always celebrated on October 12. If October 12 is a Sunday, some regions of Spain may move the celebration to Monday October 13.
Maybe because Sunday is already a holiday...?Spain's National Day and is also known as Hispanic Day or Fiesta Nacional de España or Día de la Hispanidad.

History of Spain's National Day
This national holiday honors the exact date Christopher Columbus first set foot in America.Columbus tried to find a western route to India.
After leaving the Canary Islands, Columbus' ship had been sailing west for five weeks, when on the morning of October 12, 1492, solid land was sighted for the first time.
The sighting is recorded by a "lookout", but Columbus insisted that he had seen a light from land a few hours earlier and was thus certain that he was awarded a lifetime pension from the Spanish royal family for being the first person to discover new land.They then set foot on an island in the Bahamas, which Columbus named San Salvador, but no one is sure exactly which island in the Bahamas this actually was.Columbus' voyages across the Atlantic initiated the European exploration and colonization of the Americas.

How is National Day celebrated?
A military parade in Madrid is an important part of the celebration every year. The Presidente del Gobierno (Prime Minister) has a special role in the ceremony, as he is directly under the King.
After that, a wide range of government officials, ranging from foreign diplomats in Spain to members of the autonomous governments, are invited to participate in the parade.
In addition to the big parade in Madrid, there are many other festivities that take place throughout the country.
Here it is recommended to keep track of local newspapers and notices that are posted.
All public transport, shops, banks and other offices operate as a public holiday (that is, in many cases closed) Most restaurants are open as usual.