Tu BiShvat ט״ו בשבט
The New Year of the trees—not a festival but a boundary of reckoning: from it a new year begins for the tithes of fruit.
The Mishnah opens with a list of four new years, and one of them is "the first of Shevat, the New Year of the trees, in the words of the House of Shammai; the House of Hillel says: the fifteenth." The law follows the House of Hillel.
The sense of it is entirely practical: fruit that set before this day belongs to the previous year, after it to the new one, and on that depends which tithe is taken from it. The day was chosen because by mid-Shevat most of the rains of the Land of Israel have fallen and the sap has risen in the trees.
The day has no festive rite: no Hallel is said, work is not forbidden; only one does not fast and does not say penitential prayers. The custom of eating the fruits of the Land of Israel on this day is late; the Tu BiShvat "seder" took shape among the Safed kabbalists in the sixteenth century.
On the timeline
Sources
Chazal: Mishnah, Talmud, midrash, Zohar
- Mishnah Rosh Hashanah 1:1 — the four new years and the dispute of the schools
- Rosh Hashanah 14a — why the middle of Shevat
Acharonim and later rabbinic literature
- Shulchan Aruch, Orach Chaim 131:6 — tachanun is not said
- Pri Etz Hadar — the Safed Tu BiShvat meal
Basis: Talmud and midrash.