The Old Testament tells the Jews to take a lot of days off.  It's a nightmare for employers.  But God wanted them to do a few key things:

• To worship God
• To remember how he saved them from Egypt
• To remember that he gave them the Promised Land
• To celebrate God's provision

There are Biblical holidays and Traditional holidays on the Jewish calendar today.

BIBLICAL HOLIDAYS

PASSOVER - 14th day of the first month (Leviticus 23:4-8)
A day to remember that God passed over those who put the lamb's blood on their door frame and God saved their lives in Egypt. (March/April)

FEAST OF UNLEAVENED BREAD - 15th day of the first month (Leviticus 23:4-8)
Follows right after Passover to remind the people how God asked them not to bake bread with any leaven because he was going to save them from Egypt before the bread had a chance to rise. (March/April)

FEAST OF FIRSTFRUITS - beginning of harvest/the day after the first Sabbath after Passover (Leviticus 23:9-14)
A day to celebrate the beginning of the bountiful harvest and provision of God. (March/April)  NOTE: The only holiday the Jews do not celebrate today and also the day that Jesus resurrected.

FEAST OF WEEKS/PENTECOST/SHAVOUT - seven full weeks/seven Sabbaths or 50 days from Firstfruits (Leviticus 23:15-22)
A day to celebrate the final reaping of the harvest. (May/June)

FEAST OF TRUMPETS/ROSH HASHANAH - first day of the seventh month (Leviticus 23:23-25)
A sacred assembly sand day of rest started by the blaring of a trumpet to worship God.  Today marks their New Year. (September)

DAY OF ATONEMENT/YOM KIPPUR - 10th day of the seventh month (Leviticus 23:26-32)
A sacred assembly and day of rest, including purification rites to reconnect with God. (September/October)

FEAST OF TABERNACLES/BOOTHS/SUKKOT - 15th of the seventh month (Leviticus 23:33-38)
A seven day feast of remembering how God provided and protected them while they were in the desert. (September/October)

TRADITIONAL HOLIDAYS

PURIM - celebrating Esther's heroic action of saving the Jews (February/March)
HANUKKAH - celebrating the rededication of the temple after it was defiled by the Greeks (December)
INDEPENDENCE DAY - celebrating the creation of the modern state of Israel on May 14, 1948 (April/May)

Here are links to excellent websites that explain these holidays in more detail.

http://www.agapebiblestudy.com/charts/Seven%20Sacred%20Feasts%20of%20the%20Old%20Covenant.htm

http://www.interfaithfamily.com/holidays/other_holidays/Jewish_Holidays_Cheat_Sheet.shtml?gclid=CKC03IDZxa4CFQpY7Aod1xfeUg