Year a leap year there are 366 days. A leap year occurs every fourth year, or leap year, during which a leap day is intercalated into the month of February. The name "Leap Day" is applied to the added day. The Revised Julian calendar, proposed in 1923 and used in some Eastern Orthodox Churches, has 218 leap years every 900 years, for the average (mean) year length of days, close to the length of the mean tropical year, days (relative error of 9·10). In the year 2800 CE, the Gregorian and Revised Julian calendars will begin to differ by one calendar
Joan S. Valentine Joan S. Valentine Joan Selverstone Valentine (born 1945) is a biological inorganic chemist and biochemist. Valentine's current work examines the role of transition metals, metalloenzymes, and oxidative stress in health. Her foremost expertise is superoxide anion and its functional enzyme superoxide dismutase. Valentine has been a member of the faculty of the University of California, Los Angeles since 1980, she has served as Editor-in-Chief of "Accounts of Chemical Research" since 1994, and she was elected to the National Academy of Sciences in 2005. In 1967, she graduated with a Bachelor of Arts in Chemistry from Smith College and a Ph.D.