The word for the longest measurement of time is kalpa, Hindi for
432 billion years. - A year is the time it takes for the earth
to revolve around the sun once. A calendar year is 365 days. - A
solar or tropical year is 365 days, 5 hours, 48 minutes, and 46
seconds. This year is used for most astronomical calculations. -
A sidereal year is 365 days, 6 hours, and 9 minutes. It is
sometimes used by astronomers, because it is the time it takes
the earth to return to the same place in its orbit relative to
fixed stars. - Leap year occurs every 4 years, when all the
extra hours, minutes, and seconds of the solar year are added up
to make an extra day. - B.C. means “before Christ”; A.D. means
anno Domini, Latin for “year of our Lord.” - A cosmic year is
the amount of time it takes the sun to revolve around the center
of the Milky Way, about 225 million years. Groups of Years -
Olympiad: 4 years - Decade: 10 years - Score: 20 years -
Century: 100 years - Millennium: 1,000 years - Annual: Yearly -
Biannual: Twice a ye