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February
29, 2008: Why Leap Years Are Used |
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February 29, 2008: Why
Leap Years Are Used
Timeanddate.com
The year 2008 is a leap
year. If you look at a
2008 calendar, you will
see that February has
five Fridays – the month
begins and ends on a
Friday. Between the
years 1904 and 2096,
leap years that share
the same day of week for
each date repeat only
every 28 years.
The most recent year in
which February comprised
five Fridays was in
1980, and the next
occurrence will be in
2036.
February 29, the leap
day, has been associated
with age-old traditions,
superstitions and
folklore.
What is a leap year?
A leap year is a
year in which one extra
day has been inserted,
or intercalated, at the
end of February. A leap
year consists of 366
days, whereas other
years, called common
years, have 365 days.
Which years are leap
years?
In the Gregorian
calendar, the calendar
used by most modern
countries, the following
three criteria determine
which years will be leap
years:
1. Every year that is
divisible by four is a
leap year;
2. of those years, if it
can be divided by 100,
it is NOT a leap year,
unless
3. the year is divisible
by 400. Then it is a
leap year.
According to the above
criteria, that means
that years 1800, 1900,
2100, 2200, 2300 and
2500 are NOT leap years,
while year 2000 and 2400
are leap years.
It is interesting to
note that 2000 was
somewhat special as it
was the first instance
when the third criterion
was used in most parts
of the world.
In the Julian calendar –
introduced by Julius
Caesar in 46 BC and
patterned after the
Roman calendar – there
was only one rule: any
year divisible by four
would be a leap year.
This calendar was used
before the Gregorian
calendar was adopted.
Why are leap years
needed?
Leap years are
needed to keep our
calendar in alignment
with the earth's
revolutions around the
sun.
The vernal equinox is
the time when the sun is
directly above the
Earth's equator, moving
from the southern to the
northern hemisphere.
The mean time between
two successive vernal
equinoxes is called a
tropical year–also known
as a solar year – and is
about 365.2422 days
long.
Using a calendar with
365 days every year
would result in a loss
of 0.2422 days, or
almost six hours per
year. After 100 years,
this calendar would be
more than 24 days ahead
of the season (tropical
year), which is not
desirable or accurate.
It is desirable to align
the calendar with the
seasons and to make any
difference as
insignificant as
possible.
By adding a leap year
approximately every
fourth year, the
difference between the
calendar and the seasons
can be reduced
significantly, and the
calendar will align with
the seasons much more
accurately.
(The term "day" is used
to mean "solar day" –
which is the mean time
between two transits of
the sun across the
meridian of the
observer.)
Other leap years
facts
* The Gregorian calendar
has a 400-year cycle
until it repeats the
same weekdays for every
year–February 29, 2008,
is a Friday and February
29, 2408, is a Friday.
* The Gregorian calendar
has 97 leap years during
those 400 years.
* The longest time
between two leap years
is eight years. The last
time that occurred was
between 1896 and 1904.
The next time will be
between 2096 and 2104.
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Tradition, Folklore and
Superstition
A tradition was
introduced many
centuries ago to allow
women to propose to men
during a leap year. This
privilege of proposing
was restricted to leap
day in some areas.
Leap day was sometimes
known as “Bachelors’
Day”. A man was
expected to pay a
penalty, such as a gown
or money, if he refused
a marriage offer from a
woman.
The tradition’s origin
stemmed from an old
Irish tale referring to
St Bridget striking a
deal with St Patrick to
allow women to propose
to men every four years.
This old custom was
probably made to balance
the traditional roles of
men and women in a
similar way to how the
leap day balances the
calendar.
It was also considered
to be unlucky for
someone to be born on a
leap day in Scotland and
for couples to marry on
a leap year, including
on a leap day, in
Greece. |
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