It's the traditional Scottish name for the start of the New Year. There are several theories about the origins of the name, ranging from a French New Year's greeting, "Homme est né" (Man is born), to the Anglo-Saxon Haleg Monath (Holy Month). As a Christian holiday, Christmas fell out of favour in post-reformation Scotland, and was replaced in popularity with Hogmanay, which served as the main winter solstice holiday in Scotland.
What's so different about it?
Hogmanay is all about welcoming both friends and strangers with good cheer and presents, so as to meet the New Year together and bring good fortune.
To that purpose, traditionally, it was important to start the New Year with a 'first footing'. That meant that in order to bring good luck on a house and its inhabitants, immediately after midnight, a dark-haired male bringing a gift of coal, shortbread, salt, black bun and whisky had to enter a house first. Going back to the Viking invasions, blond men were considered bad luck for a household. To enter a house giftless was also seen as rude and unlucky.
On Hogmanay, Edinburgh plays host to a grand firework display and torch procession, while in more isolated parts of Scotland, such as the Highlands and the Hebrides, Hogmanay retains some of its pagan roots, as people march around town dressed in animal skins, going from house to house to ward off evil spirits.
Also on 31 December, tradition has it that all debts should be paid off and the house thoroughly cleaned, so that 'the bells' catch you ready for a fresh start. 'The bells' mark the moment between the old and the new year, at which point everyone starts singing 'Auld Lang Syne'.
What is Auld Lang Syne about?
The most common version of 'Auld Lang Syne' nowadays is the one penned by Robert Burns, Scotland's famous poet, in 1788. However, he apparently based his poem on previous versions already in use as far back as 1700.
The song is all about remembering old friends and new in the New Year, and not forgetting the good times had by all. 'For auld lang syne' actually means 'for old times' sake', and is sung by thousands of people around the world, from Times Square to Beijing.
When singing it, traditionally, people clasp hands and form a circle, and at the beginning of the last verse, the hands go across the chest, so that you're reaching out to the neighbour on your left and vice versa. As the song ends, the circle draws together, after which there is kissing and rejoicing.
What happens this year?
In Edinburgh, there will be the traditional torch procession on 30 December from 7pm, followed by a Hogmanay street party on 31 December, which starts at 9pm and continues into the night.