Ask A Scientist General Science Archive

Question:  Will there be a February 30 in the year 2000?
 patrick j nagle

Answer 1:
No. The Julian calendar (named for Julius Caesar) assumed that the year
was exactly 365 1/4 days; that's why it added an extra day every 4 years.
(That's how we got leap years.) But the year is actually about 11 1/4
minutes less than 365 1/4 days. Over the centuries this error accumulated;
by 1582, the year in which Pope Gregory XIII introduced the Gregorian
calendar, it had grown to 10 days. Gregory simply dropped 10 days from
October 1582 and, to fix the 11 1/4 minute problem, declared that a
"century" year (that is, a year that ends in 00) is NOT to be a leap year
(even though it's divisible by 4) unless it is ALSO divisible by 400. Thus,
2000 will be a "normal" leap year. This scheme comes quite close to exactly
fixing things, but some centuries from now it will be necessary to "unleap"
a year that would otherwise be a leap year.
 rcwinther

Answer 2:
Just a small addition... the extra leap day in a leap year is February
29th, not February 30th. Normally (in non-leap year years) February
has 28 days. In a leap year, February has 29 days.  February never
has 30 days, unless the person who printed the calendar made a big
mistake.  :)
Ric (rickru)