http://en.wikipedia.org/wiki/Elijah

According to the Books of Kings, Elijah defended the worship of Yahweh over that of the more popular Baal, he raised the dead, brought fire down from the sky, and ascended into heaven in a whirlwind (either accompanied by a chariot and horses of flame or riding in it). In the Book of Malachi, Elijah's return is prophesied "before the coming of the great and terrible day of the Lord," making him a harbinger of the Messiah and the eschaton in various faiths that revere the Hebrew Bible.

The celebration is on July 20th but - being a Sunday the feast was celebrated in advance on the 17th of july this year.