Celebrated every year beginning on the 25th day of Kislev.

The dates of Hannukkah are determined by the Hebrew calendar.
The Hebrew calendar is a lunisolar calendar, which means that it follows the lunar and solar cycles instead of relying strictly on predetermined days.
This gives a very cool calendar for following nature more closely.
But for most people it’s a bit harder because it changes every year.

The date for Hanukkah is on the “regular” Gregorian calendar each year on a different date and can vary in length.
Hannukah lasts 8 days.
This corresponds with the 8 candles on the menorah, which is the famous Hanukkah candle with the 9 lights.
The light in the middle is the “attendant light”.
Each day the attendant light is lit and one candle for each day of Hanukkah.