Christmas Day and the first night of Hanukkah fall on the same date this year for the first time in nearly 20 years.
Flashback: Hanukkah last started on the evening of Christmas Day in 2005 — the only other time the two have aligned in the last 50 years.
Hanukkah has started the night of Christmas Eve twice in the last 50 years: in 1978 and 2016.
How it works: The first day of Hanukkah comes on the 25th of Kislev on the Hebrew calendar, which is based on lunar cycles with the occasional "leap month."
Jewish calendar days begin at sundown, meaning 25 Kislev starts this year on the evening of Dec. 25, when the first candle is lit.
Hanukkah can start in late November through late December on the more commonly used Gregorian calendar.
By the numbers: The earliest first nights of Hanukkah on the Gregorian calendar over the last 50 years came in 1994 and 2013, when it fell on Nov. 27.
The latest came in 1986, on Dec. 26.
The most common first night over the last 50 years? Dec. 8 (1974, 1993, 2012).
💬 Our thought bubble: This year's "Chrismukkah" is both a simple celestial coincidence and a blessing for people who take part in both holidays, giving us a rare chance to truly blend and share end-of-year celebrations and traditions with our different family groups and loved ones.
What's next: The next Hanukkah-Christmas alignment is in 2035.