Leap year

Resources

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Introduction for teachers
2012 has 366 days instead of the usual 365 - a leap year. Here is the technical reason why:

• 365 is what we call know as a normal year - the time it takes the Earth to complete its orbit around the Sun
• It actually takes 365 ¼ days so to correct this ‘error', an extra day is added to the calendar every four years

But it's not that simple because:

• The solar year is actually 11 minutes and 14 seconds less than 365.25 days
• So, after 128 years that would mean we were a whole day ahead of ourselves.

Hmm, so this is what was decided:

• Every four hundred years, three leap years are missed out. So as well as the rule that every fourth year is a leap year, a new rule said that a century year is not a leap year unless it is evenly divisible by 400.

Clear? Well, not quite, because:

• The calendar year and the solar year are still about 30 seconds different. On the plus side, it takes 3,300 years for the calendar year and solar year to differ by a day. So we can worry about this in the year 5,312.

Is it a leap year?

• A leap year can be divided evenly by 4
• Exception number one: this excludes any year divisible by 100 (so years divisible by 100 are not leap years)
• Exception number two: exception one does not count if the year can also be divisible by 400 - for example the year 2000 (so years divisible by 400 are leap years)

Introduction for children
I'm sure you've all noticed that the weather is becoming a little warmer: we seem to have left the snow behind, it's lighter in the evenings for longer, and it's even lighter in the mornings as we come to school. All in all, we're well on our way to spring. Easter is less than six weeks away, and in just 21 weeks it will be the summer holidiays... except it's going to take longer than usual this year. One whole day longer.

2012 is a special year for many reasons: it sees the Diamond Jubilee, the 60th anniversary of Queen Elizabeth's coronation; we've got the Olympics coming to Britain for the first time in 64 years; and 2012 is also a leap year.

Well, a leap year isn't as rare as the Olympics or a Diamond Jubilee but it's pretty special, too. Every four years we have an extra day in the calendar - 29th February. And that happens this Wednesday. Which makes it a very special day. Why? Because for most years February only has 28 days, but, every four years, it has 29 days.

Just think what that means if your birthday is on the 29th February: would you only get birthday presents every four years? Or maybe you'd have to stay in primary school for four times as long as everyone else - all your friends would be 44 but you'd only be 11 - because your birthday only came every four years. Imagine that!

Of course, that isn't what really happens. Anyone born on the 29th February would either celebrate their birthday on 28th February or perhaps on 1st March.

In some countries the government tells you what day you have to celebrate your birthday. For example, in New Zealand, you have to take your birthday on the 28th February; but in England and Wales, you have to take your birthday on 1st March.

Perhaps some people decide to have two birthdays instead! People who are born on 29th February even have a special name: they're called ‘leaplings'.

But why do we have an extra day in February every year?

The leap year story
We always think of the year as being 365 days long. That means Christmas day always happens in the winter when it's cold and we take our summer holidays in the summer, when it's hot.

365 days is the time it takes for the Earth to make one complete circuit, or orbit, around the sun. The Earth spins around its axis in 24 hours and this gives us day and night. But the earth moving around the sun gives us our seasons.

But here's the tricky part: it doesn't actually take 365 days for the Earth to make an orbit of the sun: it takes 365 days and a quarter. Now that may not sound like a lot, but over hundreds of years we would end up taking our summer holidays in the winter! So scientists came up with the idea of making every fourth year 366 days long. And the extra day is added in February.

In fact the Egyptians were the first people to add an extra day to the calendar but it was the Romans who decided that the day would be 29th February.

There is also a famous tradition that takes place on 19th February, that didn't arrive until hundreds of years later*. Traditionally men ask women for their hand in marriage, but on leap years, on 29th February, the roles are reversed and women are encouraged to ask men. Whoever proposes, 29th February is still a popular day to get engaged on. But if you get married on that day, you'd better decide now on which date you're going to celebrate your wedding anniversary in years to come!

* There is some disagreement about whether this tradition was invented in Victorian times, in the 1700s, or even earlier.

Conclusion
Leap years happen once every four years and for people born on that day, birthdays will always be particularly special.

Prayer
Dear Father,

Thank you for our wonderful world where inventive men and women come up with interesting solutions to everyday problems. Thank you for the people who thought up the idea of the leap year.

Amen.

Reflection
Just think of all the long and difficult calculations that would have to be made to work out that a year is not 365 days, but 365¼. How did people in ancient times manage to work that out - and how would we do it today?

Further information
In the comic operetta ‘The Pirates of Penzance' by W S Gilbert and Arthur Sullivan (1879), Frederic (the pirate apprentice) discovers that he has to serve the pirates until his 21st birthday rather than until his 21st year.