Tu B’Shevat, the 15th of Shevat on the Jewish calendar—celebrated this year on Thursday, January 16, 2014—is the day that marks the beginning of a “new year” for trees. This is the season in which the earliest-blooming trees in the Land of Israel emerge from their winter sleep and begin a new fruit-bearing cycle.
Legally, the “new year” for trees relates to the various tithes that are separated from produce grown in the Holy Land. These tithes differ from year to year in the seven-year shemittah cycle; the point at which a budding fruit is considered to belong to the next year of the cycle is the 15th of Shevat.
Tu B’Shevat is celebrated by eating fruit, particularly from the kinds that are singled out by the Torah in its praise of the bounty of the Holy Land: grapes, figs, pomegranates, olives and dates. On this day it is remembered that “man is a tree of the field” (Deuteronomy 20:19), and reflect on the lessons that can derived from botanical analogues.
Tu Bishvat will start at sunset on 15 January and will end at nightfall on 16 January). It is also called "Rosh HaShanah La'Ilanot" (Hebrew: ראש השנה לאילנות), literally "New Year of the Trees." In contemporary Israel the day is celebrated as an ecological awareness day and trees are planted in celebrate.
Courtesy of various internet sites.