When you come to the Land and you plant any food tree, you shall surely block its fruit [from use]; it shall be blocked from you [from use] for three years, not to be eaten. And in the fourth year, all its fruit shall be holy, a praise to the Lord. And in the fifth year, you may eat its fruit. [do this, in order] to increase its produce for you. I am the Lord, your God (Book of Leviticus, Kedoshim, 19:23-25).

This commandment, included in the Book of Leviticus, requires that a quite precise calendar be observed. In order to make the calculation simple and straightforward, it was agreed that its beginning will be the "common birthday of all trees" – the start of the growing season in Palestine that is traditionally considered to be the 15th day of the month of Shevat. A note about the day already appeared in the Mishnah, in the Rosh Hashanah tractate. The 15th day of the month of Shevat was considered there as one of the Jewish New Year holidays. However, it is clearly visible that for Jews living in Central and Eastern Europe this "New Year of the Trees" (Rosh HaShanah La'Ilanot in Hebrew) came in the very middle of winter.

In the Gregorian year of 2017, Tu BiShvat, or Ḥamisha Asar BiShvat, as it was earlier referred to, starts on Saturday, 11 February, at sunset. Tu BiShvat is not one of the most important Jewish holidays. Jews can work and do not have to fast on the day. 

It is believed that a regulated process of establishing the age of trees was important as Jewish farmers were obliged to sacrifice fruit in amounts dependent on the age of their trees. Biblical commentator Ramban (Nachmanides, Moses ben Nahman Girondi, 1194–1270) clarified that "the first fruit of any tree should be used to express gratitude towards God and praise his glory. Since fruit borne in the first three years is not ripe enough for the purpose, the Torah orders to use fruit borne only in the fourth year." Rashi, on the other hand (Shlomo Yitzchaki, 1040–1105) stressed that for the first three years the tree should be "sealed" and "cut off" sot that no benefit could be obtained from it. The last sentence of the quoted Torah fragment stresses the importance of the obligation. The Ha'amek Davar commentary by the Volozhin Rosh Yeshiva Naftali Zvi Yehuda Berlin (1817-1893), published in Vilnius in 1880, says: "Although I promised you great prosperity in return for observing this commandment, do not observe this only for this reason. Observe this because «I am the Lord, your God», and you wish to fulfil my will."

In the Middle Ages, a supper was organised on the holiday (seder Tu BiShvat), during which many kinds of fruit were eaten. In the 16th century, a group of mystics living in the Holy Land, Isaak Luria's followers, gave a symbolic dimension to the ceremony of consuming fruit – the produce of Israeli land. This was accompanied by reading out relevant fragments of the Pentateuch, Talmud and other scriptures as well as saying blessings over wine. In contemporary times, the custom is observed also beyond the borders of Israel. For Jews in Poland, the participation in the seder, or the festive meal, confirms their connection with the Land of Forefathers, the “land of milk and honey”. In Poland, Tu BiShvat seders are held mainly in Jewish communities, while celebrations at home are rather modest.

In the early 20th century, Jewish settlers in Palestine introduced the custom of planting trees on the occasion of Tu BiShvat. The Keren Kayemet LeYisrael fund became particularly involved in the forestation of Israel, promoting the initiative among children. It is estimated that some 2.5 million trees were planted between 1901 and 1939. In contemporary Israel, Tu BiShvat is a starting point for discussions and practical activities within general environmentalism. The tree-planting initiative, which involves school youth and teachers, is also continued. The permanent element of Tu BiShvat is the festive supper during which produce characteristic for a given region is consumed, including grains (in the form of cakes), grapes, figs, dates, olives and pomegranates.