Spain celebrates a number of important events throughout the year. Many of them are recognised as national holidays, which are commonly known as “red days”. They are similar to Bank Holidays in the UK.
Being a religious country traditionally, a lot of fiestas take place around religious events, and religious calendars, not just Christian, but other religions too.
Beyond the national holidays, each region also celebrates their own events, again, often with a religious leaning, and then there are the local holidays which are celebrated only in each of the local towns. However, some of the local holidays are celebrated at the same time in other towns too.
To complicate matters further, although many of the national holidays are date specific, repeating each year, many of the holidays move, and so the overall calendar is different each year.
The best place to find information about holidays is through the Social Security offices which operate the national system at a more local level, or through the local town halls.