Solution:
Under the Julian calendar, leap year occurred every
four years, making the average length of a year
365.25 days. That average length was too long, so
that by the middle of the sixteenth century, the
error had accumulated to more than 10 days.
Pope Gregory XIII decreed a correction to this error
in 1582, and Britain, which included the present-day
United States and Canada, made this change in 1752.
Wednesday, September 2, 1752, Julian was followed by
Thursday, September 14, 1752, Gregorian in all
countries of the British Empire.
So there was no September 10, 1752 in the United
States!
The calendar used today in the United States is
called the Gregorian Calendar Reform of 1582/1752.
It adds a day every four years (those years are
called leap years). There is an exception to the
rule. When the year is evenly divisible by 100, it
is not a leap year; but when it is divisible by 400,
it is a leap year. So 1900 was not a leap year but
the year 2000 is!
George Washington was born on February 11, 1732, by
the Julian calendar which was then in use. In 1752,
when the Gregorian calendar was adopted and 11 days
were dropped, Washington shifted his birth date in
order to keep the "real" day. That's why we now
celebrate his birthday on the 22nd.
My apologies for this "history" problem, but I
thought it was appropriate with all the talk about
Y2K and other calendar related events like when the
millenium starts. We will stick to math and logic
puzzles from now on!