Tu B'Shevat is celebrated on Monday, January 21, 2019.
Tu B'Shevat, the 15th day of the Jewish month of Shevat, is a holiday also known as the New Year for Trees. The word "Tu" is not really a word; it is the number 15 in Hebrew, as if you were to call the Fourth of July "Iv July" (IV being 4 in Roman numerals). Tu B'Shevat is the new year for the purpose of calculating the age of trees for tithing. See Lev. 19:23-25, which states that fruit from trees may not be eaten during the first three years; the fourth year's fruit is for God, and after that, you can eat the fruit. Each tree is considered to have aged one year as of Tu B'Shevat, so if you planted a tree on Shevat 14, it begins its second year the next day, but if you plant a tree two days later, on Shevat 16, it does not reach its second year until the next Tu B'Shevat.
One custom is to eat a new fruit on this day, or to eat from the Seven Species (shivat haminim) described in the Bible as being abundant in the land of Israel. The Shivat Haminim are: wheat, barley, grapes (vines), figs, pomegranates, olives and dates (honey).
Some people plant trees on this day.