About the Holy Days
The Holy Days of Adonai begin the evening before the date specified on most calendars. This is because a Jewish "day" begins and ends at sunset, rather than at midnight. Many Jews do not work or attend school on Rosh Hashanah, Yom Kippur, the first and second days of Sukkot, Shemini Atzeret, Simchat Torah, Shavuot and the first, second, seventh and eighth days of Passover.
The Feasts dates are based on the lunar calendar, and will not always fall on the same date each year.
Why We Keep Them
Col 2:16 - 17 So don't let anyone pass judgment on you in connection with eating and drinking, or in regard to a Jewish festival or Rosh-Hodesh or Shabbat. 17 These are a shadow of things
that are coming, but the body is of the Messiah...
Rav Shaul (Paul) was instructing the gentiles not to be dismayed when their families and friends shunned them for disregarding their pagan holidays and traditions in favor of keeping the 7th day Shabbat and the Feast Days of Adonai. These Feast days are a rehearsal for what is yet to come upon HIS return.
Holy Days commanded by G-d 2013
Shabbat (7th Day Sabbath)
Pesach/Matzot (Passover/Feaste of Unleavened Bread)
Bikkurim (First Fruits)
Shavuot (Feaset of Weeks)
Rosh Hashannah/Yom Turuah (Head of the Year/Day of Trumpets)
Yom Kippur (Day of Atonement)
Sukkot (Feast of Tabernacles)
Additional Jewish holidays
Purim (Feast of Lots found in the Book of Esther)
Hanukkah (Feast of Dedication)
Yom Hashoah (Holocaust Remembrance Day)
Yom Ha'atzmaut (Isreali Independence Day)