How the Biblical Calendar Works:

Years: The 12 constellations of the Zodiac were used in ancient times as the 12 "numbers" on the clock. The sun would spend approximately 1 month a year in each sign.  Usually the year began when the Sun was in the constellation Aries in the spring (Around March or April).

Months: The month began when the moon began its new phase and the first sliver of the new moon crescent is seen. By mid month it would become a full moon, and at the end of the moth turn dark again. This cycle can take 29 or 30 days.

Weeks: Weeks are not kept by the sky but instead by keeping 6 days of work and a seventh day of rest known as the sabbath, or "Shabbat".

Days: The day would change at sunset. The time between sunset and the stars appearing was seen as a mixture of day and night, this does not becme night until one can see three small stars. Often holidays will begin shortly before sunset and end the next day with three stars seen.

Leap Months: Because 12 Lunar months does not exactly match 1 solar year, an extra leap month would have to be added every few years or so in order to keep balance between the Lunar and Solar cycles.

The Planets: Besides the Sun and Moon, there were 5 other objects that appeared to wonder through the Zodiac. These were Mercury, Venus, Mars, Jupiter, and Saturn. They were used to help keep track of other periods of time such as groups of years. These were thought of as "Wandering Stars".

The Holy Days:

The Sabbath: The 7th day of the week (Saturday) is to be kept as a day of rest.

The Passover: On the night of the 14th day of the first month. the Passover meal is kept.

The Week of Unleavened Bread: Starting on the 15th day of the 1st month, during the week of unleavened bread, no bread with leaven (yeast) may be in your residence . The first day and last days are days of rest, like the sabbath. The sunday during the week of unlevened bread (Resurrection Day) is known as firstfruits. On the first day of firstfruits, we count 49 days. The 50th day is Pentecost.

Shavuot/Pentacost: 50 days after firstfruits. It is a day of rest to remember the receiving of the 10 commandments at Mt. Sinai. It is also celebrated as Pentecost, the day in which the disciples received the power of the holy spirit in the New Testament.

Fast of the 4th month (Tzom Tammuz): A daylight only fast remembering the breaching of the walls of Jerusalem during the Babylonian seige.

Fast of the 5th Month (Tisha'B'Av): A full day fast (night + day) remembering the destruction of the first and second temple.

Rosh Hashana/Yom Teruah: The main Jewish New year (There are 4 types of new years). Also known as the feast of trumpets where a horn called a shofar is blown.

Fast of Gedalia: A daylight fast in the 7th month.

Yom Kippur: The Day of Atonement, the holiest day on the calenday, and is kept with a full day (night + day) fast.

Sukkot (The week of booths or tabernacles): A week long holiday which involves dwelling in a hut outside. The first and last days are days of rest.

Shemini Atzeret/The last great day (The 8th day Assembly): A holy day concluding the sukkot week. It coincides with rerolling the Torah scroll, called Simchat Torah (The Joy of the Torah).

Hannukah: an eight day festival of lights.

Asara B'Tevet: a daylight fast in the 10th month.

Tu B'Shvat: the new year for trees.

Purim: A holiday celebrating events from the book of Esther.