Auld Lang Syne supplies the traditional midnight soundtrack for many Scottish Hogmanay celebrations.
Hogmanay is the Scottish celebration of New Year's Eve, and singing Auld Lang Syne at midnight is one of its best-known customs. The song's Scots language and themes of friendship, remembrance, and passing time fit the transition from one year to the next. Large public events and private gatherings may join hands or link arms while singing it.
Hogmanay traditions vary across Scotland. They can include torchlight processions, street parties, ceilidhs, fireworks, first-footing, and the exchange of greetings. First-footing refers to the first person to enter a home after midnight, traditionally bringing symbolic gifts such as coal, shortbread, or whisky.
Auld Lang Syne is not exclusive to Scotland or to Hogmanay. It is sung internationally, especially in English-speaking countries, and is also used at farewells and commemorations. The song is linked to Robert Burns, but its words draw on older Scottish material. Thus the answer is the song title, not the name of the festival or a Scottish national anthem.