Tu B'Shevat is a minor Jewish holiday, occurring on the 15th day of the Hebrew month of Shevat. It is also called "The New Year of the Trees." Tu B’Shevat is one of four "New Years" mentioned in the Mishnah. The name Tu B’Shevat is derived from the Hebrew date of the holiday, which occurs on the fifteenth day of Shevat. "Tu" stands for the Hebrew letters Tet and Vav, which together have the numerical value of 9 and 6, adding up to 15. Tu B’Shevat is a relatively recent name; the date was originally "Chamisha Asar B’Shvat", also meaning "Fifteenth of Shevat."

Tu B’Shevat appears in the Mishnah in Tractate Rosh Hashanah as one of the four new years in the Jewish calendar. The discussion of when the New Year occurs was a source of debate among the rabbis: "And there are four new year dates:

• The first of Nisan - new year for kings and festivals,
• The first of Elul - new year for animal tithes, as Rabbi Elazar and Rabbi Shimon say,
• The first of Tishrei - new year for calculation of the calendar, sabbatical years and jubilees, for planting and sowing,
• The first of Shevat, according to the school of Shamai; or alternatively as the school of Hillel says: the fifteenth of Shevat" (Rosh Hashana:1a). We obviously followed Hillel on this.

In the Middle Ages, Tu B’Shevat was celebrated with a feast of fruits in keeping with the Mishnaic description of the holiday as a "New Year." In the 16th century, the kabbalist Rabbi Yitzchak Luria of Safed and his disciples instituted a Tu B’Shevat seder in which the fruits and trees of the Land of Israel were given symbolic meaning. The main idea was that eating ten specific fruits and drinking four cups of wine in a specific order while reciting the appropriate blessings would bring human beings, and the world, closer to spiritual perfection. In the Chassidic community, some Jews pickle or candy the Etrog from Sukkot and eat it on Tu B’Shevat. Some pray that they will be worthy of a beautiful Etrog on the following Sukkot.

Tu B’Shevat is considered by secular Israeli Jews and organizations to be the Jewish equivalent of Arbor Day, and it is often referred to by that name in international media. Ecological organizations in Israel and the Diaspora have adopted the holiday to further environmental-awareness programs. On Israeli kibbutzim, Tu B’Shevat is celebrated as an agricultural holiday.