A leap year just accounts for the fact that earth revolves around the sun once every 365.25 days. Instead of having a quarter of a day a year, we have one every 4 years.
Mercury
For the same reason you wouldn't use a ruler to measure a paramecium. A lightyear is the distance that light travels in a year, about 6,000,000,000,000 miles. The reason it isn't used inside of our solar system is, simply, because the solar system isn't that big.
There are only leap years on Earth, so there is no such thing as a leap year on Jupiter.
In 2012 the solar system will be exactly the same. Because 2012 is just another year there's no such thing as the end of the world
saturn
The solar year has 365 days, and 366 on leap years.
One leap year of the Gregorian calendar has 12 months. One leap year of most lunisolar calendars, including the Hebrew calendar, has 13 months. A leap year is 12 months just like a common year. A leap year is longer than the solar year and a common year is shorter than the solar year by just one day.
The Gregorian and Hebrew calendars never coincide, but the Hebrew calendar does have a leap year system which is a 19 year cycle, designed to keep calendar in general sync with the solar year.
The solar year has 365 days, and 366 on leap years.
A typical solar year consists of 365 days, 1993 had 365 days. A leap year occurs once every 4 solar years and has 366 days(February has 29 days instead of the usual 28). The last leap year was 2008 and the next leap year will be in 2012.
365
In solar calendars, like the Gregorian and Julian calendars, a leap year has one more day than a non-leap year (366 instead of 365).
1950's solar system invented
They are both luni-solar calendars, based on the lunar months with leap-adjustments to stay in step with the solar year.
Both. It's lunar, with leap-months every 2-3 years to keep in step with the solar seasons.
A year with an extra day, February 29, was added to the calendar to account for the discrepancy between the solar and lunar calendars.
No, because the system of leap years that we use now did not exist then. We did not start using the current system until 1752.