Leap days are needed to keep our calendar in alignment with the Earth's revolutions around the Sun. It takes the Earth approximately 365.242189 days, or 365 days, 5 hours, 48 minutes, and 45 seconds, to circle once around the Sun. This is called a tropical year. Without an extra day on February 29 nearly every four years, we would lose almost six hours every year. After only 100 years, a calendar without leap years would be off by approximately 24 days in relation to fixed seasonal days such as the vernal equinox or the winter solstice.
Because the difference in the days is not exactly six hours, years that are divisible by 100, but not by 400, do not contain a leap day. Thus, 1700, 1800, and 1900 did not contain a leap day; neither will 2100, 2200, and 2300. Conversely, 1600 and 2000 did and 2400 will. However, this system is not perfect. Compared to the tropical year, it is off by one day every 3236 years. Today's Gregorian calendar is far more accurate than the Julian calendar which was used before 1752. When the switch was made, eleven days had to be dropped to compensate for the accumulated errors of the old calendar.
Geocachers around the world will gather to celebrate Leap Day (and earn a coveted souvenir), In Norfolk, we will gather at Wards Corner in the usual place. The event will be held at Moe's Southwest Grill. It will run from 11:30 to 12:30 on SATURDAY, February 29. The physical address is 7550 Granby St, Norfolk, VA, 23505.