fwd bisextile

[Lycidas at worldnet.att.net]

Today is the extra day in the leap year:  by Roman reckoning
yesterday was ante diem VI Kalendas Martias, and today is
ante diem bis VI Kalendas Martias.

The Oxford Latin Dictionary defines "bis(s)extum" as "The
two-day period comprising the 24th February and the
intercalary day immediately after it in leap years in the
Julian calendar."  They then cite:

cum -um kalendis est, nihil refert, utrum priore an
posteriore die quis natus sit, et deinceps sextum
kalendas eius natalis dies est:  nam id biduum pro
uno die habetur.  CELS. _dig._ 50.16.98; ULP. _dig._ 4.4.3.3

This would spoil the plot of "The Pirates of Penzance,"
which revolves around the fellow born on February 29 who
has been apprenticed until his 21st birthday.

The last bissextile day in a year divisible by 100 was
in 1600 by the Gregorian calendar (in England 1700 was a
bissextile year because the change was not made until 1752,
and in Russia 1900 was a leap year).  The last bissextile
day in a year divisible by 1000 was in the year 1000,
because
the Julian calendar was still in use, but the next one won't
be until the year 4000...maybe.  The Oxford English
Dictionary
(under "bissextile") cites one Mrs. Somerville from 1834 who
observed that "If in addition to this, a bissextile be
suppressed every 4000 years, the length of the year will be
nearly equal to that given by observation."

So will 4000 be a leap year or not?