If today, Feb. 29, is your birthday you're special.
Why we have leap year and leap day is because things just don't work out evenly in the way our solar system works and the way we keep calendars. You could also say it's the Moon's fault for creating gravitational tides and interfering with the Earth's rotation speed.
Planetary synchronization is a fascinating thing, although I doubt is many folks wonder all that much about why the earth's moon shows the same face all the time. Earth and Venus are also synchronized, with Venus always having the same face toward Earth when in closest conjunction.
Not as weird as all the myths and legends told to explain it all. Here's the ending of one that I like.
The good-minded brother taught the people the use of the plants and animals, ceremonies of thanksgiving and to live in harmony and peace. We have come to refer to him as Sonkwaiatison, "The Creator." Before departing from the Earth, he struck a deal with the people. We are to protect his gifts of Creation and be respectful of all living things, and were to simply be thankful for all that he has provided, as he has given us all that we need to live a happy life. In return for showing thanks, he would strive to keep the cycles of life continuing for the benefit of the people.
The complete story may be read here.
There are many stories of humans attempting to resolve the duality of day and night and other contradictions of the Natural world that we don't understand. We try to cram the entire universe in Yertle the Turtle's pond and claim we are King of all we can see, but it just doesn't work out. The Universe and its mysteries are bigger than our collective intellect and simply won't fit into our simplistic attempts at making Time behave according to our clock and calendar.
Suffice it to say that Leap Year and Leap Day are attempts to correct our mistakes in our calendar.
It may be that we have Presidential elections during Leap Year for exactly the same reason.
...It is a time for correcting mistakes.