Birkat Hachama (ברכת החמה, "Blessing of the Sun") refers to a rare Jewish blessing that is recited to the Creator, thanking God for creating the sun. The blessing is recited when the sun completes its cycle every 28 years on a Tuesday at sundown. Jewish tradition says that when the Sun completes this cycle, it has returned to its position when the world was created. Because the blessing needs to be said when the sun is visible, the blessing is postponed to the following day, on Wednesday morning. According to Judaism, the Sun has a 28-year solar cycle known as machzor gadol (מחזור גדול, "the great cycle"). A solar year is estimated as 365.25 days and the "Blessing of the Sun", being said at the beginning of this cycle, is thus recited every 10,227 (28 times 365.25) days. The last time that it was recited was on April 8, 2009 (14 Nisan 5769 on the Hebrew calendar.) From an astronomical point of view, there is nothing special to these dates; e.g. the sun, moon, planets and stars will not be aligned in any specific pattern. The text of the blessing itself is as follows: Source of the practice The primary source for the institution of Birkat Hachama is a Beraita mentioned in the Talmud: The middle of this clause in the beraita (elided here) speaks of other astronomical phenomena, the interpretation of which is ambiguous. The Gemara clarifies when the 'turning point' (תקופה) mentioned in the beraita occurs: Next, the gemara explains the basis of the 28 years: This explanation provided by Abaye is based on a ruling of Shmuel also mentioned in the Talmud:<ref>Bavli Eruvin 56a</ref> Shmuel stated: The vernal equinox occurs only at the beginning of one of the four quarters of the day, either at the beginning of the day or at the beginning of the night, or midday or midnight. The summer solstice only occurs either at the end of 1.5 or at the end of 7.5 hours of the day or the night. The autumnal equinox only occurs at the end of 3 or 9 hours of the day or the night. The winter solstice only occurs at the end of 4.5 or 10.5 hours of the day or the night. The duration of a season of the year is no longer than 91 days and 7.5 hours. Shmuel's calculations, however, are imprecise because the