What are the 12 days after Christmas for?

by Amber Bower and Gemma Kerr


From your computer

Who for

Adults and families

Whether you celebrate Christmas or not, it’s hard to ignore how much this holiday affects life in Britain in December. There is a big festive lead up of gathering presents, preparing all the food, and then, it all abruptly comes to an end. For some, the important bit is yet to come - the 12 days of Christmas. For others, if we’re lucky, we can enjoy some time off between Christmas and the New year (if we can keep track of what day it is!).  

The presents given by your true love on each of the 12 days of Christmas, according to the popular song.  Image Credit: Xavier Romero-Frias


You might think of the 12 days of Christmas as purely a Christian tradition, but many cultures have paid close attention to these 12 days that fall over the New Year. Germans have their Rauhnachte, Greeks call this time Callikantzaros, and here in the UK Celts have observed this time as the Omen days. And all of this has much more to do with science than you might expect.  It’s all about space, time, and something called a lunisolar calendar.  So why are the 12 days after Christmas special?

Simply put, it’s because we have some time left over.

What is a lunisolar calendar?

There are a lot of ways to count time.  We divide our calendars into years, months, and days – and this has a lot to do with the arrangement of objects in our solar system.

For ancient folks, one of the easiest ways to count time was to link it to objects in the sky. The day is the clearest example of this. We know a new day has begun when the sun rises into the sky again.  Similar systems can be used for longer stretches of time.

In many calendars, the month is based on the moon. The moon cycles through its phases over 28 days (roughly) – and the different shapes are easy to spot. So, by looking at the moon, you could tell which day of the month it is. Of course, this only works if everyone agrees that the new month starts with the new moon. Calendars that work like this, based on the moon, are called lunar calendars. If a lunar calendar follows the idea of the year consisting of 12 months, aka cycles, it will count to 354 days (also roughly). A great example of this is the Islamic Hijri calendar.

Phases of the moon.  The different shapes are easy to recognise in the sky.  Image Credit: NASA/Bill Dunford 


However, one downside of using a lunar calendar is that it falls out of sync with the movement of the sun. It takes 365 days (roughly) for the earth to orbit the sun. This means that the seasons drift in the lunar calendars – slowly changing which months will fall in which season.

To get around the slight variations we experience when observing objects in the sky, many calendars include extra bits of time in the year to account for the difference. This is what a leap-day is for. But there are also leap-months in some calendars. Or, in some cases, an extra 12 days were added to the 12 moon cycles for the calendar year to align with the sun.

So lunisolar calendars are simply calendar systems which account for the movement of both the sun and moon.


Where does the 12 days of Christmas fit in?

The celebrations at this time of year go back well before the birth of Christ. Before the arrival of the Romans, much of the UK and Ireland were inhabited largely by Celtic communities. For centuries they lived on the land spanning from what we now know as Northern Scotland to Western Ireland, and across Wales and England.

The Celts’ seasons were divided into two parts ‘darkness’ and two parts ‘light’. They began their year with ‘darkness’.  On October 31st they celebrated Samhain as the end of the ‘light of Harvest’, and the beginning of a New Year.

In December, Celtic tradition doesn’t celebrate the birth of Christ but the Winter Solstice - which falls just a few days before. The Winter Solstice marks the shortest day of the year, and the longest night. The proximity of these important dates in Celtic and Christian traditions speaks to how intertwined these histories are.

The Coligny Calendar: a Celtic calendar made in France 2nd Century CE


The Celts saw the passing of the Winter Solstice as an opportunity for rebirth. The passing of the longest day meant the following days could only get longer and lighter. As they were using a lunisolar calendar, they still needed to account for the 12-day difference between the moon cycles and earth orbiting the sun. They called these extra 12 days the Omen Days.

Omen Days (in Welsh ‘y coeldyddiau’), starting on December 26th and ending on January 6th, hold a very special place in the Celtic calendar. Some see this time as the ‘extra piece of time’ in the lunisolar calendar.

This ‘extra piece of time’ begins just after Christmas, and there are 12 days in total. A lot of us refer to this extra time by another name: The 12 Days of Christmas. Yes, those 12 days of Christmas … the ones with the True Love bearing extravagant gifts like leaping lords, dancing ladies and various birds.



What can I do with this extra time?

This Celtic version of the 12 days of Christmas, the Omen Days, are seen by some as a time to go into nature to contemplate the future. You might look for an omen each day that would directly relate to a month in the following year.

December 26th would present an omen that foretold the month of January.

December 27th would predict for February. 

December 28th for March… ending with January 6th reflecting the following December. 

Omens could be anything – spotting an animal on your path, or an interesting pattern in the clouds. It is a ritual that is practised very little nowadays, but some communities in Wales and Ireland still touch on the tradition. One message from practitioners is clear though. You’ll know an omen if you see one, and only you can interpret its meaning.

A toad spotted recently by We The Curious staff.  An omen of good things hopping into our future?  Image Credit: Paul Cornish


Why is it that, as a science centre, we are publishing an article talking about rituals and omens?... I hear you ask.By sharing this Celtic tradition, we encourage you to use it as a prompt to take yourself (and anyone around you) out into nature. It can be a difficult time of year for many people, and for many reasons.  A lot of us have experienced low-mood or lack of energy as the year comes to an end. Other than waiting for your true love to send you a partridge in a pear tree, what is there to do with this time?

Making this choice to go into nature every day for twelve days, even if only for 5 minutes, can boost your energy, creativity and focus. There is a Japanese term for going into nature as a form of meditation; Shinrin Yoku - which translates to forest bathing. There are indications that Shinrin Yoku can decrease the stress hormones in your body, improve symptoms of depression and anxiety and elevate your quality of sleep.

As well as reaping these benefits, why not also take in what appears around you? Take note of a bird, the colour of the bark on the leafless trees, is there fog in the air?

Whether your predictions come true or not, at least you’ve used this time to explore nature – a routine that you can carry into the new year. (You don’t have to wait for the first of January to begin those resolutions!) 

We all have traditions, rituals and routines. Some are passed down, some are intentional and some become subconscious. Over this winter period, why not take the time to enjoy the nature around you? Maybe you’ll discover a new tradition or even a good omen for the future.

What might you find if you step outside?


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