in what century was halloween first introduced?

Halloween was first introduced in the ancient Celtic festival of Samhain, which dates back around 2,000 years ago. This places its origins roughly in the 1st century BC to 1st century AD, which is in the 1st century CE (Common Era). Samhain marked the end of the harvest season and the beginning of winter, and it was believed that on this day, the boundary between the living world and the spirit world was thinnest, allowing spirits to cross over. The festival included lighting bonfires and wearing costumes to ward off ghosts, and over time, these customs evolved into the Halloween celebrations known today.