Chanukah celebrates the re-dedication of the Second Temple of Jerusalem during the second century B.C.
A group of Jewish rebels, known as the Maccabees triumphed against their foreign oppressors who had defiled the temple by erecting an altar to Zeus, and sacrificing pigs within its sacred walls.
In order to rededicate the temple, the seven-lamped menorah that always burned within the temple at all times had to be lit. There was only enough oil to last for one day.
Miraculously, the oil burned for eight days, leaving time to find a fresh supply of oil.