Before Halloween 2021, it is recommended to create a Halloween-based Calendar with all the event details properly marked and shared with your family members. You can create a Halloween Calendar 2021 using EdrawMax Online as it offers online team collaboration, allowing your friends and family to enter the data virtually. As the below Halloween Calendar 2021 suggests, Halloween's origins date back to the ancient Celtic festival of Samhain (pronounced sow-in). The Celts, who lived 2,000 years ago, mostly in the area now Ireland, the United Kingdom, and northern France celebrated their new year on November 1st.