The leap day is the day that falls on 29 February. The leap day occurs every four years when the leap year is observed. As a rule, leap years occur every four years in order to adjust for the extra time of 1/4th of a day that each year looses according to the revolution of the earth. This was implemented from as long back as 48 BC when Julius Caesar decreed the Julian calendar. That time lost is compensated once in four years with an extra day, the day we know as the leap day. The year in which the leap day falls is called leap year.
However, in 730 AD it was discovered that the 1/4th of the day was exactly 674 seconds too long, which could be compensated by adding an additional day in a circle of 128 years. Though it was accepted as truth no official correction had been made, and this mistake was carried forward for 800 years.
Pope Gregory XIII in 1582 ordered the implementation the Gregorian calendar when this mistake was rectified by reducing 10 in the month of October, i.e. October 4th was read as October 15th and made up for the miscalculation. Keeping the extra time in mind, it was calculated that every 400 years it would be needed to add three days. Hence, leap years would fall on all years that end with double zero, with the exception of those years which are not divisible by 400.
There is no big deal with this day, other than it occurs every four years and due to this, it relatively rare. People who are born on this day have to celebrate their birthdays every four years instead of every year. For some this is a pain - especially for children who look forward to their birthday so much. But for women, who are so sensitive about their age, it is so wonderful. The leap day can literally make women ageless. Many people also believe that those who are born on 29 February are extremely lucky and will achieve great fame in their lives. To tell the truth, I believe in this superstition, because the few people (about six) I know born on this day, all with absolute no exception are doing extremely well, leading prosperous and happy lives.
On the other hand, the leap day has created a few inconveniences in application in modern machinery like watches, computers, etc where the machine measures time without being manned and adjusted by man. Automatic watches which indicate date need to be programmed carefully so that every four years they show 29 February before going to 1 March. In the same league are digital cameras and other automatic measuring devices which change dates automatically. Computers have come out with specialized chips which can rectify the possible malfunction, and the twenty-first century will have a permanent solution to the application of the leap day effect.
The leap year is also the time to celebrate life. If you are born on this year you are considered special, especially if it is on the leap day. Your birthday does only come every four years, so if you take that into consideration, you will be still young. It can also be a slight dilemma as you don't really know when to celebrate your birthday.