The greatest error in one-year algorithms for solar declination tends to occur at the equinoxes in leap years. Declination varies by 0.3 degrees from year to year during the leap year cycle on a given day near the equinox, and by about half of this in midsummer and midwinter. There is also a limit to the accuracy in which the continuously-varying declination can be calculated from the day number. The maximum change in solar declination through twenty-four hours is about 0.4 degrees and occurs at the equinox, when the declination is close to zero. Very precise values of declination are rarely required in daylighting calculations but can be obtained, for a particular time of day and year, from almanacs such as the Nautical Almanac(1). Roy and others(2) compare the accuracy of several algorithms, and also list a four-year algorithm. The formula below is correct within 0.0007 radians (0.04 degrees) except near the equinoxes in leap years, when the error is 0.0014 radians (0.08 degrees)