Why do we celebrate New Year on 1 January?

Each new year is celebrated with fireworks and celebrations around the world.

But how did January end up being the first month of the year? It wasn't always the case.

We go back 2,000 years to find out the origins of our current calendar and how it changed over the centuries in Europe as Christianity took hold.

Thanks to Jacco van Loon from Keele University's observatory and Professor Diana Spencer, Department of Classics, Ancient History and Archaeology, University of Birmingham.