Birkat Hachama (ברכת החמה, "Blessing of the Sun") refers to a Jewish blessing that is recited on the Sun once every twenty-eight years, when the vernal equinox as calculated by tradition falls on a Tuesday at sundown.
According to Judaism, the Sun has a 28 year solar cycle known as machzor gadol (מחזור גדול, "the large cycle"). A solar year is 365.25 days long and the "Blessing of the Sun", being said at the beginning of this cycle, is therefore recited every 10,227 (28 times 365.25) days. The next time that it will be recited will be on April 8, 2009 (14 Nisan 5769 on the Hebrew calendar).
The same blessing is recited upon experiencing various natural phenomena, including lightning, comets, and meteor showers; as well as upon witnessing wondrous natural topography, such as great mountains, rivers and vast wilderness. When recited for these other experiences, the blessing is recited alone without additional verses or Psalms etc.
"ברוך אתה ה' אלוקינו מלך העולם עושה מעשה בראשית"
"Blessed are You, LORD, our God, King of the Universe who makes the works of Creation."