This year marks the first time since 2005 that the first night of Hanukkah falls on the same day as Christmas.

Christmas and Hanukkah both always fall on the 25th, but in two different months: Christmas falls on December 25th in the Gregorian calendar and Hanukkah begins on the 25th day of the month of Kislev in the Jewish calendar.

The start date of Hanukkah in the Gregorian calendar varies from year to year because the Jewish calendar is based on lunar and solar calendar cycles. According to Chabad, the months in the Hebrew calendar follow a lunar cycle that lasts about 354 days. In order not to fall behind the solar calendar, which has around 365 days, there is a 13th month in the Jewish calendar every few years, which represents a “leap year”.

Another difference is that in the Jewish calendar, the holiday begins at sundown and continues until the next day, so Hanukkah, which lasts eight days, begins a few hours after Christmas begins this year.

According to the Jewish Federations of North America, Hanukkah and Christmas have coincided only a few times since 1900. They began on the same day in 1910, 1921, 1959 and 2005. Rabbi Joshua Stanton, vice president for interfaith initiatives at the Jewish Federations of North America, sees this as an opportunity for learning, collaboration and togetherness.

“The goal is not proselytizing; it’s about learning deeply from each other,” Stanton said in a statement to CBS News. “Others see you the way you see yourself.”

Rabbi Moshe Hauer, executive vice president of the Orthodox Union, said he sees the convergence of holidays as an opportunity to appreciate the diverse religious landscape in the United States

“We have learned that we must work hard to protect this, especially at a time of increasing anti-Semitism and other forms of hate,” Hauer told CBS News in an email.

The convergence of holidays also presents unique opportunities and challenges for interfaith families. Some people celebrate what is known as “Chrismukkah,” a name derived from the overlap of the holidays and made popular by the television series “The OC.”

“I think, especially as Hanukkah is seen as a kind of Jewish Christmas, we’re seeing more and more interest in how they might correspond to each other. Both holidays are about light and the presence of God in dark times. Candida Moss, professor of theology at the University of Birmingham, told CBS News 24/7. “And of course this represents a great opportunity for interfaith families to celebrate both traditions side by side.”

Rabbi Rick Jacobs, president of the Union for Reform Judaism, said he believes each holiday should be given its due and not mixed together, “because I think that detracts from the uniqueness of each one.”

“But proximity can actually make us understand more, appreciate people of different faiths more and bring more light to what is often a very dark time of year,” Jacobs told “CBS News 24/7.”

According to Hebcal, the two holidays will coincide again in 2035 and 2054.

It is also rare for Hanukkah to begin on Christmas Eve. This has happened twice in the last 50 years: in 1978 and 2016.