Why do we have leap year?

Every leap year we welcome February 29 into our calendar - and with good reason. The humble leap day comes and goes every four years without much fuss - but it saves us a lot of trouble and is the one day women are encouraged to propose to their man.

Professor of Applied Physics at the University of Liverpool Ken Durose told the ECHO: “Leap years are a way to avoid a good deal of confusion – and some inconvenient party times.

“Without leap year we would only celebrate New Year on the stroke of midnight once every four years. The next year we’d have to celebrate at 6am, and after that at midday then the year after at tea time.

“I’ve spoken to some of the people in the lab and they weren’t too keen on having a 6am New Year ’s Eve, you’d run out of steam by then.”

We need an extra day every fourth February because a solar year is 365.25 days – not 365, so an extra day is added to keep the calendar and solar years in sync.

Without February 29 every four years the seasons would, in time, fall out of sync with the calendar.

Dr Steve Barrett from the Department of Physics at the University of Liverpool said: “If we adopt a calendar which is always exactly 365 days long then over a long period of time the calendar will slowly slip out of step with the Earth moving around the Sun. And so the seasons will occur at different times of the calendar year.

“After 100 years the seasons will have shifted by 25 days and after 400 years the shift will have amounted to 100 days. The middle of winter would then be in April and the middle of summer in October.

“To stop this happening we add a leap day into February in every fourth year. This year is exactly divisible by four and so 2016 is a leap year. This keeps the calendar in step with Earth’s motion and so the seasons come and go at the same time every year.”