Today is Constitution day in Spain, which happily means a national holiday. This day marks the day in 1978 when a new constitution for Spain was approved. It marks the transition from Franco's dictatorship to democracy (democratic monarchy) in Spain.
Here in Catalunya it means very little more than a day off work. In some places there are regular celebrations, while others take this as a day on which to demonstrate against the state.
The day does mark the start of the December festivities, being the first of national holidays this week, in the lead up to Christmas. Although it is officially a national holiday many shopping centres and supermarkets etc will be open to cash in on the pre-Christmas consumerism.