Hanukkah, the Festival of Lights, celebrates the rededication of the Temple in Jerusalem after it was defiled by the Syrian Greeks in the 2nd century BCE. Hanukkah almost always comes in December, when the days are shortest and the nights are darkest.
Hanukkah celebrates liberation from oppression, and reminds us of the importance of freedom of religion. It also teaches us to fight back when people's rights are taken away.