Happy Bissextile

First Posted: 1/15/2009

Today is the 29th day of February, which doesn’t stumble upon us that
often — about every four years, with an exception every four centuries.
The calendar that Julius Ceasar gave us in 46 B.C. deserves credit for
this additional day in February, Leap Day, less well-known as
Bissextile, which basically means two days in one. Ceasar’s calendar,
which evolved into what we use today, the Gregorian calendar, assumed
that a year had 356 1/4 days, meaning that there was an extra day to be
accounted for with each passing of four years. This was necessary
because the four seasons and astronomical events do not perfectly align
with a 365-day year. That’s why some months have 30 days, others have 31
and February has 28, except, as we said, every four years, when it
swells by a single day — and complicates the birthday celebration for
those among us who arrived on a Feb. 29th. Bissextile is needed to keep
the calendar in line with the stars and the seasons, since the stars and
seasons stubbornly refuse to align themselves with the calendar. You
might remember, however, that when the new millennium arrived, there was
no Bissextile. That’s because in A.D. 730 an Anglo-Saxon monk discovered
that Ceasar’s year was 11 minutes and 14 seconds too long, which adds up
to an extra day every 128 years. But nothing was done about it until
1582, by which time the calendar was 10 days off. Pope Gregory XIII
fixed that by decreeing that day Oct. 4 would be Oct. 15, therefore
correcting the clock. To allow for future adjustments, it was decided
that forever more, years ending in “00” would be common years — all the
years other than leap years — except those divisible by 400, which 2000
was. You will not have to worry about this again in your lifetime. If
you find yourself thoroughly confused, we understand, and you are
probably in a large club. But enjoy Bissextile. It will be your only
chance to do so until Feb. 29, 2012.

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