All Jewish holidays begin the evening before the date specified. In Hebrew calendar a "day" begins and ends at sunset, rather than at midnight. All holidays are celebrated on the same day of the Hebrew calendar every year (with few exceptions when some holidays fall on Shabbat).
Tishrei 1-2 - The Jewish New Year. Marks the beginning of ten days of repentance culminating with Yom Kippur.
Tishrei 10 - The Day of Atonement.
Tishrei 15 - Sukkot commemorates the forty years of wandering of the People of Israel in the desert after the exodus from Egypt. In memory Jewish people are commanded to build and live in temporary dwellings for seven days (Leviticus 23:33).
Tishrei 22 - Simhat Torah (Joy of Torah) marks the completion of the annual reading of the Torah. The concluding section of Torah is read followed by the reading of the first section of Genesis, symbolizing the continuing annual cycle of weekly Torah reading.
Kislev 25 - Hanuka celebrates the rededication of the Temple in Jerusalem after the victory of the Maccabees over the Hellenistic (Greek) army.
Shevat 15 - Tu Bishvat is also known as the New Year for Trees.
Adar 14 - Purim commemorates the annulment of the decree against the Jewish people in ancient Persia (Late 6th century B.C.E.).
Nisan 15 - Passover commemorates the Exodus of the people of Israel from ancient Egypt.
Nisan 27 - Holocaust Memorial Day in remembrance of the 6 million Jews killed by the German Nazi regime and their collaborators.
Iyar 4 - Memorial Day in memory of the fallen soldiers of the Israel Defense forces and victims of Arab terrorism.
Iyar 5 - Israel Independence Day. Marks the Declaration of Independence of the State of Israel in 1948.
Iyar 28 - Jerusalem Day celebrates the liberation of Jerusalem during the Six-Day War.
Sivan 6 - Shavuot commemorates the giving of the Torah and the Ten Commandments to Israelites at Mount Sinai over 3000 years ago. Shavuot means "weeks" as Torah was given 7 weeks after the Exodus from Egypt. First harvest was brought to the Temple on Shavuot.
Av 9 - Fast of the Ninth of Av in Hebrew calendar commemorates the destruction of the first and second Temples (the first by the Babylonians in 586 B.C.E.; the second by the Romans in 70 C.E.). Expulsion of Jews from Spain in 1492 also falls on this date.