vernal equinox has been shifting slightly forward in the Gregorian year ever since 1582. In 1609, the halachic vernal equinox was on April 4 In 1709, the halachic vernal equinox was on April 5 In 1809, the halachic vernal equinox was on April 6 In 1909, the halachic vernal equinox was on April 7 In 2009, the halachic vernal equinox was on April 7 In 2109, the halachic vernal equinox will fall on April 8 In 2209, the halachic vernal equinox will fall on April 9 In 2309, the halachic vernal equinox will fall on April 10 The halachic equinox usually jumps a day every century because the algorithm that established the Gregorian calendar dictates that leap years do not occur in years divisible by 100, unless also divisible by 400. Jewish law, however, provides no means for changing the established calendar until such a time as the Sanhedrin might be reconvened, and compensates for it by moving the date of the equinox almost every century. There was no shift between 1909 and 2009, however, because of the exception regarding years divisible by 400; thus, the year 2000 did contain a February 29 and no compensation was necessary. The table at right depicts all the vernal equinoxes from 1981 to 2009, two years in which Birkat Hachama occurs; note that the equinox does not occur at sunset (time=0) on the fourth day (Tuesday) any other years in the entire 28-year cycle. The halachic year of 365.25 days is equivalent to 52 weeks, 1 day and 6 hours. This means that any given date will, three times out of four, appear a day later in the calendar week in a subsequent year. For example: July 3, 1932 was on Sunday July 3, 1933 was on Monday July 3, 1934 was on Tuesday July 3, 1935 was on Wednesday July 3, 1936, however, was on a Friday and not a Thursday because the six hours that accrued over each of the four years effectively adds another calendar day (i.e. 6 hours × 4 years = 24 hours = 1 day).Halacha maintains that the Sun was created in the position of the vernal equinox immediately after sundown on the fourth day of the week of Creation, which is equivalent to sunset on Tuesday of that week. If that is considered time zero (t=0), and subsequent years' vernal equinoxes occur one day and six