Shavuot

the 5th day of Sivan , fifty days after Passover (Jewish world)
　
The Yom Tov begins at sundown of the 5th day of Sivan, exactly fifty days after Passover .

Shavuot, the Feast of the Weeks, is the Jewish holiday celebrating the harvest season in Israel. Shavuot, which means "weeks", refers to the timing of the festival which is held exactly 7 weeks after Passover. Shavuot is known also as Yom Habikkurim, or "the Day of the First Fruits", because it is the time the farmers of Israel would bring their first harvest to Jerusalem as a token of thanksgiving.
Shavuot also commemorates the anniversary of the giving of the Ten Commandments to Moses and the Israelites at Mount Sinai.

Many of the traditions and customs of Shavuot have evolved from the legends and stories describing the experiences of the Israelites at Mount Sinai. According to tradition the Israelites actually overslept on the morning of God's visit. To compensate for this negligence, Jews hold a vigil on the eve of Shavuot. They stay awake from dusk to dawn, keeping themselves busy with the readings of the Torah  and the Talmud. A digest of readings has evolved called Tikkun Leil Shavuot, the "Restoration of Shavuot Eve," which includes selections from the Torah, the Prophets, the Talmud, and the Zohar.

Another Shavuot custom is the eating of dairy foods. One explanation states that this comes from a passage in the Torah which reads: "And He gave us this land, a land flowing with milk and honey".

Another explanation comes from a legend stating that before the visit from God the Jews did not keep kosher or follow the Kashrut (dietary) laws. It was on this first Shavuot that they found out that their utensils were nonkosher and thus unfit for use. So finding themselves without kosher meats or utensils the Israelites were forced to eat only dairy foods. Today Jews celebrate Shavuot by eating blintzes, cheesecake, and other dairy dishes.

Another legend tells the story of the Israelites finding Mount Sinai blooming and lush with greenery and flowers. From this legend grew the custom to decorate the Jewish home and synagogue with tree branches and flowers. Some temples decorate the Torah scrolls with wreaths of roses.

Notes:

Sivan: n. 息汪月，即犹太教历三月，犹太国历九月，在公历五、六月间，共三十天                      
Passover: n. 犹太教的逾越节
Moses: n. 十戒，犹太教、基督教的戒条          
Mout Sinai: 西奈山，基督教《圣经》中记载的上帝授予摩西十戒之处
vigil:值夜，守夜
the Torah:  律法，圣经旧约之前五卷
the Talmud: 犹太法典
the Zohar: 《光明篇》，犹太教神秘主义对摩西五书的注疏
kosher:  指食物、食品店等合理的，符合犹太教规戒律的
blintz: n. 一种热薄饼
greenery: n. 绿树；绿色植物
synagogue: n.  犹太教会堂