On Tuesday, April 8, we celebrate Birkat Hahama, the Blessing over the Sun. It’s observed once every 28 years, when the sun reaches the exact location that it did when it was created.
Jews actually also recite a Blessing over the Moon, too. This occurs at night, of course, and it happens once every month — and, for that reason, is not nearly as interesting and obscure and cool-sounding.
There might be another reason that we only celebrate Birkat Hahama once a generation, however. Check out the beginning of this article, wherein one rabbi is arrested by brave Policeman Foley — in Tompkins Square Park, one of New York’s punk-rock meccas, no less! — and another, that tricky Rabbi Klein, flees the scene.