Both Halloween and Hallowe’en are dictionary-accepted forms of the day when children dress up and knock on doors asking for candy. As an official holiday, it should always be capitalized, even when it is used as an adjective. The apostrophe spelling is more common outside the United States.
History
Most know that Hallowe’en is a contraction of All Hallows’ Evening, but what you may not know is that the day originated with the Celtic calendar, which marked the first day of the year as November 1st. When the Catholic Church named November 1st All Saints’ Day or All Hallows, October 31st became All Hallows’ Eve, like Christmas Eve. And like Christmas, All Saints’ Day can be called Hallowmas.
Examples
For the TV host and face of David Jones, Halloween is the year’s major party night. “I didn’t know how important it was until I went to live in the US,” he says. [Sydney Morning Herald]
Of these families, the total for Halloween spending is expected to be around $11.3 billion this year – an impressive number hard to ignore for retailers in the Halloween business. [Forbes]
As a child growing up in the Forties and Fifties, we always scooped out turnips to make our Hallowe’en lanterns; when I moved south, it was swede lanterns for my own children. [The Telegraph]
Visitors to the event are being asked to dress up as there will be prizes for the best Hallowe’en costumes, while a variety of fairground rides will help to keep the little ones entertained. [Linlithgow Gazette]
This year, Halloween and Christmas décor seem to have been simulcast. (I’d call it Hallowmas but that’s taken, a.k.a. All Saints Day on Nov. 1.) [The Spectrum]