Tu BiShvat (Hebrew for the 15th day of the Hebrew month of Shvat) is the new year of the trees.
Tu BiShvat, called the "New Year of the Trees," falls at a seemingly incongruous time of year.
Tu BiShvat is a minor festival whose provenance dates only to the time of the Second Temple. However, the kabbalists who clustered around the great fifteenth-century mystic Isaac Luria of Safed placed great weight on the holiday, creating new festivities, gatherings at which hymns were sung, fruit (particularly carob) was eaten, and four cups of wine were taken (as in the Passover seder).
Sukkot, the Jewish festival of booths (a harvest holiday of thanksgiving), begins on the 15th day of the Hebrew month of Tishrei.
On the Jewish calendar, holidays begin in the evening, at sundown, and they continue through the next day.
A sukkah is a temporary, hut-like dwelling built during the holiday of Sukkot. (In fact, the word sukkot is the plural of sukkah.)