I have attached a pdf of the Biblical Calendar.
The Divine Calendar consists of a weekly Sabbath, monthly "new moons" (marking the beginning of each month), 7 yearly or annual sabbaths and their associated days, a year long land sabbath every seven years, and a year long sabbath and "jubilee" every 50 years.
The new moons were a time keeping method, identifying when each month began in order to keep track of when each of the annual feasts began. Individuals were not required to do anything on the new moons, that was purely something for the priests to keep track of as printed calculated calendars did not exist. The new moons did however sometimes become a handy excuse for people to have a "mini feast" (see for example
1 Sam 20:5), but this was not required by God.
The yearly feasts were:
First month -
Passover and the
Feast of Unleavened Bread
Third month -
Firstfruits (Pentecost)
Seventh month -
Day of Trumpets,
Day of Atonement, and
Tabernacles and the
Last Great Day
In the
first month (Abib, occurring in the spring), the 14th day was the day of the Passover, when the Passover lambs were slain and cooked. The next day, the 15th day of the first month, was the First Day of the weeklong feast of Unleavened Bread. This day was a sabbath, as was the last day of Unleavened Bread (the seventh day of the feast, which was the 21st day of the month Abib). The intervening days between the First and the Seventh Day of Unleavened Bread were not sabbaths.
In the
third month was the Feast of Firstfruits. It is called Pentecost (meaning 50th) because of the way in which its date was determined. On the morning after the sabbath of the first day of Unleavened Bread, an omer (a sheaf, a small sample) of the firstfruits were brought to the Temple and waved by the priest. From that day, one counted 50 days. That 50th day was the official feast of the Firstfruits, when the harvest was complete. This day was also a sabbath.
In the
seventh month several things took place. The month was announced (as all months were) by the blowing of trumpets at the sighting of the first visible crescent of the new moon. In the seventh month, this announcement took on a special significance, as it heralded the seventh month in which occurred the Day of Atonement and the Feast of Tabernacles. This day was a sabbath, and was commemorated by loud noisemaking throughout the land.
The 10th day of the seventh month (ten days after Trumpets) was the Day of Atonement. This day was a sabbath, and was also a mandatory fast day. It is the only fast day God commanded for His people.
The 15th day of the seventh month was the first day of Tabernacles, and was a sabbath. The remaining six days of the week of Tabernacles were not sabbaths. The feast of Tabernacles was also the fall harvest festival.
The day after the last day of Tabernacles, known as "the Last Great Day", was a sabbath. This day was the 22nd day of the seventh month. Although it was not technically part of the Tabernacles festival, because it occurred the day after the last day of Tabernacles, it obviously is joined to it much as Passover is joined to the weeklong feast of unleavened Bread.
A
sabbath is a rest day and set apart to God. No ordinary labor is to be performed (your regular daily work, whether your job or household chores, or business related work, or projects that would constitute "work"). For the weekly Sabbath, cooking and food preparing was supposed to take place the day before (the "Preparation"), so that cooking and meal making would not have to be done on the weekly Sabbath. However, the annual sabbaths have an allowance for food preparation (you can cook on those days). This is due to the fact that occasionally one of the annual sabbath days would occur either the day before or the day after the weekly Sabbath. In which case you would have two consecutive days which were both sabbaths. So rather than requiring people to either go hungry on one of those days, or else make three days worth of food on the day before the sabbaths began, God simply said we can make food on the annual sabbath days (except of course for Atonement, which as mentioned was the annual fast day, or on a weekly Sabbath if the annual sabbath and the weekly one fell on the same day). After all, these are feasts, meant to be celebrated not just by individuals but by families and groups of people. That means lots of food, and that requires food preparation.
These feasts are just that -
feasts. They are
festive occasions, meant to be celebrated with eating. Think traditional Thanksgiving, Christmas, or Easter celebrations. They are
sabbaths, so they are days of rest. No mowing the yard, doing the laundry, reporting to the office, etc. Also no requiring others to do such (any employees one might have, one's work animals, or frequenting businesses for the purpose of transacting business, etc). They are
holy convocations, meaning they are meant to be occasions for the faithful to gather, pray, and worship God.
Some notes about how each feast was kept:
Unleavened Bread - prior to the start of this feast, all the leaven was collected and removed from the house. Anything containing leaven was likewise removed from the house. Either eaten, burned, or thrown away. So that during the seven days from the 15th day of Abib to the 21st day of Abib no leaven was in the house and no leavened food was eaten.
Tabernacles - keeping this feast involved the construction of a sukka (plural "sukkoth"), a temporary dwelling place, a booth or tabernacle. Basically a tent. The instructions include the gathering of branches and limbs of "goodly trees" for the use in the construction of the booth or tabernacle, and essentially "living" in the booth for seven days. This can be as complete as actually moving in to the booth, or as simple as eating meals in the booth each day. The idea is to spend time in the tabernacle.
A note about
rabbinical rules: The rabbinics made up tons of various rules and regulations for the weekly Sabbath, the annual sabbath feast days, etc. These rules included such inventions as the "sabbath day's journey", prohibition against handling musical instruments, prohibitions against handling money, two fast days per week (instead of the one annual fast commanded by God), specific prayers and various washings and pourings of water, specific regulations regarding the "correct" construction of a booth, etc etc. None of those rules were given by God, and are not binding on Christians.