Birkat Hachama (ברכת החמה, "Blessing of the Sun") refers to Jewish blessing that is recited to thank G-d 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 therefore recited every 10,227 (28 times 365.25) days. The last time that it was recited was on April 8, 2009