The Shehecheyanu blessing ws introduced to encourage Jews to offer thanks for new and unusual experiences. It it typically recited atthe beginning of holidays and to celebrate special occasions.
Baruch atah adonai eloheinu melech ha'olam shecheyanu v'kiy'manu v'higyanu lazman hazeh.
Source: Kolatch, Alfred J. The Second Jewish Book of Why. NY: Jonathan David Publishers, 1989 and Cardin, Rabbi Nina Beth. The Tapestry of Jewish Time. NJ: Behrman House, 2000.