Leap Year...

Leap Day: February 29, 2012

’Leap Day’ is February 29, which is an extra (intercalary) day added during a Leap Year, making the year 366 days long – and not 365 days, like a common (normal) year.

Nearly every 4 years is a Leap Year in our modern Gregorian Calendar.

Brief history of the Leap Day
Leap Years are needed to keep our calendar in alignment with the Earth's revolutions around the sun. It takes the Earth approximately 365.242199 days (a tropical year) to circle once around the Sun. If we didn't add a day on February 29 nearly every 4 years, we would lose almost six hours every year. After only 100 years, our calendar would be off by approximately 24 days!

Leap Years 2008 – 2032

Year February 29 – day of the week
2008 Friday
2012 Wednesday
2016 Monday
2020 Saturday
2024 Thursday
2028 Tuesday
2032 Sunday

The ancient Roman Calendar added an extra month every few years to maintain the correct seasonal changes.

But Julius Caesar implemented a new calendar – the Julian Calendar – in 45 BCE (Before Common Era) with an extra day added every 4 years. At the time, Leap Day was February 24, because February was the last month of the year.

What's a Leap Second?

February 30 was a real date

Too many Leap Years
In 1582 Pope Gregory XIII refined the Julian calendar with a new rule that a century year is not a Leap Year unless it is evenly divisible by 400. This transition to the Gregorian Calendar was observed in some countries including Italy, Poland, Portugal, and Spain. The transition took longer for other countries; Great Britain started using the Gregorian Calendar in 1752 and Lithuania in 1915.
infor from http://www.timeanddate.com/date/leap-day.html

more infor:
http://www.projectbritain.com/year/leapyear.htm