Halloween is celebrated on October 31, as a cultural Anglo-Saxon festival. It originally stated 2.500 years ago as a Celtic manifestation to celebrate the end of summer, every October 31st of our yearly calendar (Samhain).
It was believed that when cattle was guided back into the stables, at the beginning of winter, spirits would come out of their graveyards and come back to life by invading the bodies of the human beings.
Spirits would ask for food first and that’s the origin of the so common "Trick or Treat” that represented the spirit’s threat to take over someone’s body.
In order to avoid this, Celts painted their houses and ornamented them with bones and skulls, and hoped that they could scare the spirits away.
These are the origins of the tradition that today leads us to ornament our houses with scary things and to dress up in costumes. In this way, this ended up being a festivity associated to the arrival of the pagan Gods to life.
The Catholic Church decided to embrace this festivity, stating All Saints’ Day on November 1st. In England, it was called "All Hallows' Day" and the previous night "All Hallows' Eve" that lately became "Halloween".
The festivity was then exported to USA by European immigrants during the XIX century, and started to be massively celebrated in 1921, when the first Halloween parade was celebrated in Minnesota and then other states started to join into the celebration.
Halloween finally became an international celebration by the end of the 70’s and the beginning of the 80’s, mainly due to the influence of the cinema and TV.
Currently, the young kids wear a costume every October 31st and walk through the streets, knocking doors and asking for sweets. After knocking on a door, they regularly state "Trick or treat".
If they receive sweets, money or any type of compensation, the treat is accepted. If they don’t, kids do some trick.