When Is Samhain Really? The Moon, the Calendar Change and Old Halloween

When is Samhain? The fixed date, the Moon, the sky and the forgotten Old Halloween

When is Samhain? Most calendars say 31 October, and that is a good answer. But the old Celtic year followed the Moon, Britain lost eleven days in 1752, and some villages kept Halloween on 11 November well into living memory. Here is the honest history of the date, and four ways to keep Samhain in 2026.

When Is Samhain, and Why 31 October?

Samhain, said SOW in, is the old Gaelic festival at the start of winter. By the time it was written down in Irish stories, from around the ninth century, it was tied to the start of November.

It begins on the evening before because the Celts counted time by nights. Julius Caesar noticed this about the Gauls: they measured time by nights rather than days, so a festival began at sunset. That is why Samhain is kept on the evening of 31 October and runs into 1 November.

The Christian calendar fixed the same moment. All Saints fell on 1 November across much of Europe by the ninth century, and the night before became All Hallows Eve, Halloween. Whatever the deeper past, for well over a thousand years the start of November has been the anchor.

The date on the calendar is old. The question is what lay underneath it before anyone wrote it down.

Did Samhain Once Follow the Moon?

This is where it gets interesting. The calendars of the ancient Celtic world were tied to the Moon, not to fixed dates.

The Roman writer Pliny the Elder, describing the druids gathering mistletoe in the first century, says the ceremony was held on the sixth day of the moon. He adds that this day marked the beginning of their months and their years. You can read the passage in translation in Philip Harland’s collection of ancient sources on the Celts.

Ancient writers usually counted a month from the first thin crescent, so the sixth day falls close to the first quarter Moon. If a druid style month began that way in November 2026, it would start in the middle of the month, around the first quarter Moon at 11.47am on Tuesday 17 November.

So the idea that the earliest Samhain moved with the Moon is reasonable. What we cannot do is prove the exact rule, because no Irish source from before the conversion tells us how they set the date.

The Coligny Calendar: Less Certain Than You Have Heard

The Coligny calendar is a bronze tablet made in Roman Gaul around the second century and found in 1897 at Coligny in eastern France. It is the longest piece of Gaulish writing we have, and it is a true lunar calendar: twelve months of 29 or 30 days, with an extra month added every two and a half years to keep the Moon in step with the seasons.

One month is called Samonios, and it is often linked to Samhain. You will read online that the calendar proves the Celtic year began at Samhain. The scholars are far less sure.

• Some place Samonios at the start of the winter half of the year, around October and November.
• Others place it at the start of the summer half, around May and June, closer to Beltane.
• The researcher Helen McKay, who has studied its thousands of markings, argues that the calendar began at the equivalent of Beltane, and that a famous entry often read as the three nights of Samhain means something else. Her summary is on her research page on the Coligny calendar.

The honest picture is this. The Coligny calendar proves the Gauls kept a careful lunar year with a month named Samonios. It does not prove when Samhain fell, or that it began the year.

The Eleven Lost Days of 1752

Now the part almost nobody mentions. For centuries Britain and Ireland used the Julian calendar, which drifted slowly away from the seasons. Most of Europe had moved to the more accurate Gregorian calendar in 1582, but Britain held out.

When Britain and its lands, Ireland included, finally switched in 1752, eleven days had to go. Wednesday 2 September 1752 was followed straight away by Thursday 14 September.

That moved every fixed festival eleven days earlier in the season. The 31 October of today falls eleven days earlier in the solar year than the 31 October your great great grandparents’ great grandparents knew. In the old reckoning, our Samhain eve would have been 20 October.

Put the other way round, the old 31 October landed on the new 11 November. And some people refused to move.

Old Halloween on 11 November

Across rural Britain and Ireland, people kept their festivals on the old dates for generations. Old Christmas Day on 6 January is the best known. Halloween had an old date too.

A recording in the School of Scottish Studies archive describes Halloween in Killin, Perthshire, being held on 11 November until around 1914, the old date. It was a full Samhain night: a bonfire on the hill, built from timber gathered over weeks, guisers going round the houses in disguise, mischief in the gardens, and girls trying divination to see who they would marry. You can find it in the Tobar an Dualchais archive.

So Old Halloween on 11 November is not a modern idea. It is a real date, kept by real communities, within living memory of our great grandparents.

Astronomical Samhain: Following the Sun

The fourth date comes from the sky. Samhain sits roughly halfway between the autumn equinox and the winter solstice, so many people today mark the exact midpoint, when the Sun reaches 15 degrees of Scorpio. In 2026 that is Saturday 7 November.

This is a modern way of reckoning, and there is no written evidence the ancient Irish used it. But the landscape hints at an interest in this season. At the Hill of Tara, the passage of the Mound of the Hostages lets low sunlight into its chamber on mornings in early November. Whatever the builders intended, the light still arrives around this time of year, more than five thousand years later.

It is also worth noticing that the astronomical date sits close to Old Halloween. Before 1752, the calendar date and the sky were nearer together. The eleven lost days pulled the fixed festival earlier, away from the midpoint.

Four Ways to Keep Samhain in 2026

There is no single true date that anyone can prove. What we have are four honest choices, each with its own roots, and in 2026 they all fit inside twelve days.

Traditional Samhain: Saturday 31 October

The date carried by the Irish records, Halloween and living tradition. Keep it from sunset, as the old night counting did. Light a candle, say the names of those you remember, and let the evening be quiet.

Astronomical Samhain: Saturday 7 November

For anyone who follows the Sun. Revisit your altar as the Sun reaches the midpoint of the dark season, and notice what has settled since the 31st.

Lunar Samhain: Monday 9 November

The New Moon in Scorpio at 7.02am, with the dark moon the night before. The closest we can come to a Moon led Samhain, in the sign of endings and depth. Set one quiet intention for the winter. Our New Moon in Scorpio 2026 guide has a ritual for it.

Old Halloween: Wednesday 11 November

For anyone who loves the old ways. Light a small fire or a single candle, and remember that people in Perthshire were still doing exactly this on this night barely a hundred years ago.

Many people simply keep the whole stretch as a Samhain season. Our Samhain 2026 guide sets out a gentle fortnight ritual that runs from the clocks going back to the new moon.

A simple Samhain candle for any of the four dates

1. As the light goes, set a dark stone such as black obsidian beside a single candle.
2. Light the candle and say aloud which Samhain you are keeping, and why.
3. Speak the names of those you are remembering, one at a time.
4. Name one thing the year has finished with, and put it down.
5. Let the candle burn a while, then snuff it rather than blowing it out.

Never leave a candle burning unattended. A black or white Manifest Magic chime candle burns down in a single sitting, which suits a short ritual.

Quick Questions About When Samhain Is

When is Samhain 2026?

Samhain is kept on the evening of Saturday 31 October 2026, running into Sunday 1 November. Astronomical Samhain is Saturday 7 November and lunar Samhain is the New Moon in Scorpio on Monday 9 November.

Is Samhain always on 31 October?

The traditional date is fixed at 31 October into 1 November. The astronomical and lunar dates change each year, usually falling in the first half of November.

What is Old Halloween?

Old Halloween is 11 November, the date the old 31 October fell on after Britain and Ireland dropped eleven days in 1752. Some communities, such as Killin in Perthshire, kept Halloween on 11 November until the early twentieth century.

Did the Celts celebrate Samhain at the new moon?

Celtic calendars were lunar, and Pliny says the druids began their months on the sixth day of the moon. But no early source tells us exactly how Samhain was dated, so a new moon Samhain is a reasonable modern choice rather than a proven ancient rule.

What is astronomical Samhain?

The moment the Sun reaches 15 degrees of Scorpio, halfway between the autumn equinox and the winter solstice. In 2026 it falls on Saturday 7 November.

Dates and Moon times in this post are UK time. Moon times follow the Royal Observatory Greenwich. Historical sources are linked where they appear.