Halloween is already here, but many don’t know where it actually originated from. This is the day those of pagan religion and those who practice Wicca look forward to all year.

Samhain comes from ancient Celtic traditions and was typically celebrated over 2,000 years ago by those in the pagan religion. It’s a three-day celebration of the end of summer and it’s believed that the curtain in between the physical world and the spirit world is let down during this time, Time reports.

In Celtic traditions, this time of year was to welcome the dark half of the year. Their year was split up between light and dark months. Ireland, Scotland, the U.K. and other parts of Europe were the destinations of this celebration.

Pagans practice their religion based on the wheel of the year. There are ceremonies, rituals, fire festivals and solstice celebrations throughout the year. For modern-day pagans/witches, Halloween is the day they look forward to all year.

Modern-day Halloween is thought to have come from this celebration.

“The practices of this fire festival evolved over time...many of Celtic traditions were reframed with a Christian narrative in an attempt to capitalize on the popularity of the pagan practices while spreading the new religion. That reframing created many of the Halloween traditions that people still participate in today,” according to Time.

Those who still celebrate the Samhain holiday took to Twitter to wish everyone a happy Samhain.

One user said, “Blessed be all my Wiccans, Pagans and Witches by the the Goddess and the God on another full cycle of the wheel of the year. Happy Samhain.”

Another tweeted, “Happy #Samhain, perhaps one of the most important pagan holidays. Today is a day for important family and friends, thanking for everything in the past year, and preparing for the upcoming year. Stay safe and have a blessed holiday!

Back in the 5th century, those of the Christain faith tried to completely reframe this holiday and called it, “All-hallows’ Eve,” according to History.com. This is what Halloween is today and those pagan traditions were never done away with.

Samhain
The two-day Celtic celebration is extremely similar to Halloween. In this image, people take part in a sunset ceremony on the lower slopes of Glastonbury Tor as they celebrate Samhain at the Glastonbury Dragons Samhain Wild Hunt 2017 in Glastonbury Somerset, England, Nov. 4, 2017 Getty Images/Matt Cardy