Chanukah begins at sundown

Chanukah is the Jewish eight-day, wintertime “festival of lights,” celebrated with a nightly menorah lighting, special prayers, and special foods.

In the second century BCE, the Holy Land was ruled by the Seleucids (Syrian-Greeks), who tried to force the people of Israel to accept Greek culture and beliefs instead of mitzvah observance and belief in the Lord. Against all odds, a small band of faithful but poorly armed Jews, led by Judah the Maccabee, defeated one of the mightiest armies on earth, drove the Greeks from the land, reclaimed the Holy Temple in Jerusalem, and rededicated it to the service of the Lord.

When they sought to light the Temple’s Menorah (the seven-branched candelabrum), they found only a single cruse of olive oil that had escaped contamination by the Greeks. Miraculously, they lit the menorah and the one-day supply of oil lasted for eight days, until new oil could be prepared under conditions of ritual purity.

To commemorate and publicize these miracles, the sages instituted the festival of Chanukah. At the heart of the festival is the nightly menorah lighting. The menorah holds nine flames, one of which is the shamash (“attendant”) which is used to kindle the other eight lights. On the first night, just one flame is lit. On the second night, an additional flame is lit. By the eighth night of Chanukah, all eight lights are kindled. Special blessings are recited, often to a traditional melody, before the menorah is lit, and traditional songs are sung afterward. A menorah is lit in every household (or even by each individual within the household) and placed in a doorway or window. The menorah is also lit in synagogues and other public places.

(from https://www.chabad.org/)