It's Halloween!
Halloween was originally influenced by the Celtic culture. The word Halloween is a contraction of "All Hallows' Evening", which is the day before All Saints' Day. Halloween is famous for its carved pumpkins called Jack-o'-Lanterns. Today, Halloween is mainly celebrated in the United States, Great Britain, Ireland, Canada, and Australia and has also began spreading to other European and Asian countries.
Source: http://en.wikipedia.org/wiki/Halloween