1st time almost ever Hanukkah & Thanksgiving share same date | not again for about 70,000 years
Hanukkah commemorates the Jewish people’s successful rebellion against the Greeks in the Maccabean War in 162 BCE. A ritual cleansing and re-dedication of the Temple occurred after the Jewish people’s victory. It is believed that there was only enough consecrated oil to keep the lamp burning for one day but the small bottle of oil miraculously lasted for eight days. Hanukkah, also known as Chanukah, is referred as the Feast of Lights or Festival of Lights for this reason.
The reason for this year's rare alignment has to do with quirks of two calendars, the Gregorian and Jewish calendars. Much of the world follows the Gregorian calendar, which has a 365-day year based on the Earth's orbit around the sun, with leap years every four years. The Gregorian calendar was implemented by Pope Gregory to keep Easter in line with the season it was originally celebrated in. But the Jewish calendar follows the waxing and waning of the moon.
Jews aren't the only ones who follow a lunar calendar. The Muslim calendar is also based on the cycles of the moon, but Muslims don't adjust their calendar, meaning that holidays can shift seasons over time. The Celts used a combination solar and lunar calendar, and Hindus from different regions of the world have several solar and combined solar and lunar calendars. The Maya calendar, meanwhile, used three different cycles, only one of which was tied to a 365-day year.