Cherry Blossom Viewing (花見, Hanami) is the traditional Japanese custom of viewing Sakura (Cherry Blossoms) which bloom nation-wide from mid January to early May. The event lasts a week or two.
Flower viewing festivals consist of having an outdoor party beneath the sakura trees during day, sometimes these parties go on until late at night. Hanami at night is called yozakura (夜桜, night sakura). In many places such as Ueno Park, temporary paper lanterns are hung for the purpose of yozakura.
The custom is said to have started during the Nara Period (710–794). Initially devoted toward Ume blossoms, by the Heian Period (794–1185), Sakura blossoms came to attract more attention and hanami became synonymous with sakura.
Sakura blossoms were initially believed to divine the year's harvest and announce the rice-planting season. Believing that spirits lived inside the trees, the devotees made offerings. Emperor Saga adopted this practice and held flower-viewing parties with sake and feasts underneath the sakura trees in the Imperial Court in Kyoto.
The custom was originally limited to the elite of the Imperial Court, but soon spread to samurai society and, by the Edo period, to the common people. Tokugawa Yoshimune planted areas of cherry blossom trees to encourage this.
Today, the Japanese people gather in great numbers wherever the flowering trees are found. Thousands of people fill the parks to hold feasts under the flowering trees. In more than half of Japan, the cherry blossoming period coincides with the beginning of the scholastic and fiscal years, and so welcoming parties are often opened with hanami.