The Fulfilled Feasts of Israel
Jan 9, 2018
The 7 Jewish Feast Days And Their Prophetic Significance
The Feasts of the Lord
Dec 14, 2013
One very exciting way that the Christian can “watch” for Christ’s return is in recognizing and understanding the Feasts of the Lord, as detailed for us within Leviticus 23. This is a fascinating study, but it is one, unfortunately, that most Christians are unaware of. Will He return to find you watching?
|Also See Should Christians Celebrate the Jewish Feasts?
ON THIS PAGEIntroduction
The Weekly Sabbath and The High Sabbaths
Overview of The Seven Feasts of IsraelThe First Four Feasts
1. Pesach or Passover
2. Unleavened Bread
4. Shavuot the Festival of WeeksThe Remaining Three Feasts
5. Rosh HaShanah or The Feast of Trumpets
6. Yom Kippur or The Day of Atonement
7. Sukkot or The Feast of BoothsThe Eighth Festival
It was the only ritual observance instituted in the Ten Commandments and, even in modern Judaism, is considered extremely important, being a day of not only rest, but of prayer and spiritual enrichment – “a day of great joy eagerly awaited throughout the week, a time when we can set aside all of our weekday concerns and devote ourselves to higher pursuits.” 
The Sabbath was (and is) observed every week from sundown on Friday to sundown on Saturday, and has a two-fold significance. 1) It is a remembrance of creation, inasmuch as the Israelites were to imitate God’s example and rest on the seventh day. 2) It is also meant to be a remembrance of the nation’s deliverance from the bondage of Egypt.
1. So the sons of Israel shall observe the Sabbath, to celebrate the Sabbath throughout their generations as a perpetual covenant.’ “It is a sign between Me and the sons of Israel forever; for in six days the Lord made heaven and earth, but on the seventh day He ceased from labor, and was refreshed.” (Exodus 31:16-17 NASB)
2. ‘You shall remember that you were a slave in the land of Egypt, and the Lord your God brought you out of there by a mighty hand and by an outstretched arm; therefore the Lord your God commanded you to observe the Sabbath day.” (Deuteronomy 5:15 NASB)
Remembering that they were once slaves in Egypt, they were to give themselves and their bond-servants a day of complete rest (Exodus 20:10) – radical concepts in ancient times.
but the seventh day is a Sabbath of the Lord your God; in it you shall not do any work, you or your son or your daughter, your male or your female servant or your cattle or your sojourner who stays with you. (Exodus 20:10 NASB)
No work was done, nor did anyone fast on the Sabbath, since it was considered a day of joy. Meals, cooked the day previous, were often more elaborate and eaten more leisurely.
The High Sabbaths While the regular Sabbath was a weekly occurrence, there were seven annual or High Sabbath days, which did not necessarily fall on a Friday-Saturday. These High Sabbaths were related to the annual feast days as listed in Leviticus 23.
For example, the first and last days of the seven day Feast of Unleavened Bread, the day of Pentecost (Shavuot), The Day of Trumpets (Yom Teruah or Rosh HaShanah), The Day of Atonement (Yom Kippur), and the first day of the seven day Feast of Tabernacles (Succoth) were all High Sabbaths. The Passover and the Feast of First Fruits were not.
Although they are referred to in several places in the Bible, only Leviticus 23 lists all seven feasts in chronological order. Note: The feasts are celebrated on the same day of the Jewish calendar every year, but since the Jewish year is not the same length as a solar year on the Gregorian calendar used by most of the western world, the date shifts on the Gregorian calendar. Details
The historic and prophetic significance of the Feasts is one of the most fascinating of all Biblical studies. Although believers are not required to keep them, every Christian should be very familiar with the Feasts, as they not only celebrate a historical event in Israel’s past but are also a prophecy of future events that concern us all. They were types that, in Christian theology, are actual historical events that were a rough draft or a glimpse, of one or more events yet to occur. These subsequent happenings (the antitype) were certainly much more important than the original type.
However, that the significance of the antitype was not always obvious at the original occurrence is clearly shown by the fact that the Jews did not realize that the feasts were not solely related to past historical events (For example, Passover called to mind the night the angel of death passed over the Jewish houses that had been marked with the blood of a lamb, but did not spare the houses of the Egyptians that were not).
However, at the time they were given, every single one of the feasts pointed to something incomprehensibly bigger that was yet to come. They were were types – symbols of – the first and second coming of the promised Messiah. In fact, and quite fascinatingly, God’s entire plan of salvation for mankind from start to finish, is outlined by these feasts, which were also related to Israel’s agricultural seasons. The Spring and Summer Feasts signified the commencement of redemption, while the Fall Feasts signify its culmination.
“The first three feasts Passover, Unleavened Bread, and First Fruits occur in rapid succession in the spring of the year over a period of eight days. They came to be referred to collectively as “Passover.”
The fourth feast, Harvest, occurs fifty days later, at the beginning of the summer. By New Testament times this feast had come to be known by its Greek name, Pentecost, a word meaning fifty.
The last three feasts Trumpets, Atonement, and Tabernacles extend over a period of twenty-one days in the fall of the year. They came to be known collectively as Tabernacles.” 
The first four feasts have already been fulfilled. The first two by Jesus Christ on the actual feast days according to the Hebrew calendar… He was sacrificed on Passover, and resurrected on the Feast of First Fruits. The third Feast of Unleavened Bread had great significance in light of His sacrifice, while the Fourth Feast Shavuot, or the Festival of Weeks was again fulfilled on the exact day of what we now call Pentecost.
While we certainly do not know exactly how the other three feasts will be fulfilled, it is reasonable to surmise that they will also be fulfilledon the actual feast day.
NOTE: It is hugely important to pay attention to the fact that the Feasts (that symbolize a sequence of events) were given by God in a set chronological order. Therefore the events that they symbolize will take place in the same exact order. I have read way too many interpretations of the Feasts that jump backwards and forwards between them in an effort to make them fit into pre-conceived end time scenarios. What we need to do is make the order of the Feasts our guideline to coming events, instead of scrambling them to fit our ideas.
1) Pesach or Passover:
The Jews had been slaves in Egypt for generations, but were refused their freedom despite plague after plague being visited on them by the Almighty through Moses. However, the final straw that caused the Pharaoh to change his mind came when, after weeks of back and forth, the Israelites were given very explicit instructions – They were to sacrifice a lamb and put some of the blood on the door posts and lintels of their homes. That night the angel of God “passed over” the houses of the Jews that marked by the lamb’s blood, but caused the death of the first-born of all families in the houses that were not. (Exodus 12)
On the 10th of Nisan, Jesus rode into the city of Jerusalem on the very day the lambs to be slaughtered were selected. What was not understood by the Jews was that He entered the city as the sacrificial Lamb chosen by God. Four days later Jesus was crucified on the day of preparation for the Passover which was when the lambs were actually slaughtered. See John 19:14.
The Passover lamb was to be a “male without defect” which is how Jesus was described.
knowing that you were not redeemed with perishable things like silver or gold from your futile way of life inherited from your forefathers, but with precious blood, as of a lamb unblemished and spotless, the blood of Christ. (1 Peter 1:18-19 NASB)
Additionally, unlike most people who were crucified Jesus’ bones remained unbroken. It was customary to break the leg bones of the person after a few hours of crucifixion so that the person could not push up with their legs in order to breathe. Breaking the legs ensured that death by asphyxiation followed very quickly. However, while the Romans broke the legs of the two thieves crucified on either side of Jesus, they did not touch Jesus who was already dead. (John 19:31-34)..
And, in yet another testimony to the Divine origin of the Scriptures, many centuries earlier one of the Old Testament stipulations for the Lamb eaten on the Passover was that none of it’s bones were to be broken.
“It is to be eaten in a single house; you are not to bring forth any of the flesh outside of the house, nor are you to break any bone of it. (Exodus 12:46 NASB)
However the full extent of the symbolism is only realized when viewed from a Christian perspective. When John the Baptist …
… saw Jesus coming to him and *said, “Behold, the Lamb of God who takes away the sin of the world! (John 1:29 NASB)
Paul reiterated this when he said “… For Christ our Passover also has been sacrificed” (1 Corinthians 5:7 NASB)
Just as the destroyer “passed over” every home protected by the blood of the lamb, so God will “pass over”, or not execute judgment on every believer protected by the blood of the lamb Jesus. This is called Salvation
The feast of Unleavened bread began on the 15th of Nisan (the day following Passover) and continued for seven days. The first and last days of this week long festival were High Sabbaths. The day prior to a High Sabbath was commonly known as a ‘preparation day’ which meant the Passover on the 14th of Nisan was also the preparation day for the “High Sabbath” on the 15th.
The Egyptians urged the people, to send them out of the land in haste, for they said, “We will all be dead.” So the people took their dough before it was leavened, with their kneading bowls bound up in the clothes on their shoulders. (Exodus 12:33-34 NASB)
Note that at least six Biblical passages (Exodus 12:14-20; 13:6-8; 23:15; 34:18; Leviticus 23:6; Deuteronomy 16:3, 8) mention the prohibition of leaven during the seven days of the Feast. The consequences of using any leaven were severe.
‘Now this day will be a memorial to you, and you shall celebrate it as a feast to the Lord; throughout your generations you are to celebrate it as a permanent ordinance. ‘Seven days you shall eat unleavened bread, but on the first day you shall remove leaven from your houses; for whoever eats anything leavened from the first day until the seventh day, that person shall be cut off from Israel. (Exodus 12:14-15 NASB)
Even modern day Jews who observe the traditional feasts go through a thorough search of their houses for any form of leavened food (chametz) every last crumb of which is removed. This because, in the Bible, leaven always symbolized an evil influence of one kind or another. Both Jesus and Paul warned about leaven…
And Jesus said to them, “Watch out and beware of the leaven of the Pharisees and Sadducees.” (Matthew 16:6 NASB) Also See Luke 12:1
And He was giving orders to them, saying, “Watch out! Beware of the leaven of the Pharisees and the leaven of Herod.” (Mark 8:15 NASB)
“Your glorying is not good. Know ye not that a little leaven leaveneth the whole lump? [1Corinthians 5:6]
The sons of Israel present in Jerusalem celebrated the Feast of Unleavened Bread for seven days with great joy, and the Levites and the priests praised the Lord day after day with loud instruments to the Lord. (2 Chronicles 30:21 NASB)
Thus the sons of Israel who were present celebrated the Passover at that time, and the Feast of Unleavened Bread seven days. There had not been celebrated a Passover like it in Israel since the days of Samuel the prophet; nor had any of the kings of Israel celebrated such a Passover as Josiah did with the priests, the Levites, all Judah and Israel who were present, and the inhabitants of Jerusalem. (2 Chronicles 35:17-18 NASB)
But one has to wonder why leaven was used as a symbol of evil. This is probably because of the character and process of leavening, which is based on fermentation. Given time, the yeast reproduces, spreading throughout the dough or batter, biologically changing the chemistry of the dough as it works. Sin, like leaven, has a polluting quality. It doesn’t stay small or contained for very long, but quickly spreads. As Paul asked the Galatians who were turning from the truth of the Gospel to doctrine preached by false teachers.
You were running well; who hindered you from obeying the truth? This persuasion did not come from Him who calls you. A little leaven leavens the whole lump of dough. (Galatians 5:7-9 NASB)
But now Christ has been raised from the dead, the first fruits of those who are asleep. For since by a man came death, by a man also came the resurrection of the dead. For as in Adam all die, so also in Christ all will be made alive. But each in his own order: Christ the first fruits, after that those who are Christ’s at His coming, (1 Corinthians 15:20-23 NASB)
There some controversy as to the timing of this event. The Scriptures say the wave offering was made “on the day after the Sabbath”. Orthodox Judaism takes the position that it is the day following the “High Sabbath”, which was the first day of the seven day feast of Unleavened Bread. Others believe that it was the day after the regular Sabbath that fell during the seven day feast.
However, John 19:31 tells us that this particular Sabbath was a “high day” – one of the seven annual High Sabbath days
Then the Jews, because it was the day of preparation, so that the bodies would not remain on the cross on the Sabbath (for that Sabbath was a high day), asked Pilate that their legs might be broken, and that they might be taken away. (John 19:31 NASB)
Remembering that the Jews counted their days from sundown to sundown, the likely scenario was that Jesus was crucified on Wednesday, and rose three days later after nightfall on Saturday evening when the regular Saturday Sabbath was over and the festival of First-fruits had begun… “on the day after the Sabbath”.
However, here is yet another fascinating detail. The day Jesus was resurrected on the feast of first-fruits was when Mary Magdalene crying at the tomb, heard and recognized Jesus’ voice and turned to Him. But, Jesus told her not to touch Him “for he had not yet ascended to the Father”. Instead He asked her to go to His brethren and tell them that he was ascending to His and their Father and God. (John 20:17)
Why wasn’t Mary Magdalene allowed to touch Jesus?
The contemporary Jewish historian, Josephus revealed that during the Feast of First Fruits the Jews were not even allowed to touch the harvest until the First Fruits had been presented to God at the Temple.
Jesus had to present Himself to the Father before He made any human contact..
The word Pentecost (Gk. pentekoste) means fiftieth. It occurred on the fiftieth day, after the festival of First-fruits which was when the Messiah was resurrected.
In the New Testament, the disciples were commanded to tarry at Jerusalem for “what the Father had promised” (Acts 1:4) which they did. They did not have long to wait. The coming of the Holy Spirit occurred on the next Jewish holiday when Jews from different parts of the country came to Jerusalem to celebrate Shavuot or the completion of the harvest season. In other words, it was on Shavuot that the disciples were transformed from timid, fearful men into bold preachers of the word and when the first of the harvest came in, ie. on Pentecost about three thousand Jews heard the Gospel, believed and were baptized.
It is entirely possible that the two loaves of bread were brought to the temple on Shavuot (See verse 17 above) represented the two groups – Jew and Gentile – both of whom were part of the Harvest..
As a side note, this Feast was called Yom Teruah in the Old Testament, but is now commonly called Rosh HaShanah that literally means “head of the year” and is celebrated as the Jewish New Year. I have read that the change of name came about because of a Babylonian influence, but that does not answer the question of how New Years day can fall on the first day of Tishri, the seventh month of the Hebrew calendar when Sukkot or The Feast of Tabernacles (Ingathering) that occurs fifteen days later is said to be the end of the year
“Also you shall observe the Feast of the Harvest of the first fruits of your labors from what you sow in the field; also the Feast of the Ingathering at the end of the year when you gather in the fruit of your labors from the field. (Exodus 23:16 NASB)
It is now largely celebrated for two days, although the observance of a second day is a later addition. Anyway what is is now called and how it is now celebrated is of little consequence.
However, so far all the feasts have symbolized a sequence of events in chronological order. Jesus’ Crucifixion (Passover), The removal of sin (Unleavened Bread), The Resurrection (First-fruits), Pentecost (the Festival of Weeks). This makes it very unlikely that Rosh HaShanahwill be fulfilled by the Rapture, which is not the next event scheduled to take place on the end time calendar as much as some people may hope (and endeavor to prove) it does.
See The Rapture (Part V of The End Of The Age) for the reasons the Pre-Tribulation Rapture is a wishful thinking.
The first day of every month was begun with the blowing of trumpets, but there was deeper significance attached to the blowing of trumpets on Rosh Hashanah – the first day of the seventh month. Rosh Hashanah heralded the beginning of the period known as the High Holy Days with Yom Kippur (The Day of Atonement ) occurring ten days later, on the tenth of the month. The ten days from Rosh Hashanah to the Day of Atonement (both inclusive) are known as “the days of awe”, a time of national repentance for Israel. It was a time of penitence, prayer, and fasting, in preparation for the Feast of Tabernacles. This period was a far cry from the times of communal celebrations of events (such as Passover and Purim).
Three books are opened in heaven on Rosh Hashanah, one for the completely wicked, one for the completely righteous and one for those in between. The completely righteous are immediately inscribed in the book of life. The completely wicked are immediately inscribed in the book of death. The fate of those in between is suspended until Yom Kippur. If they do well, they are inscribed in the book of life. If not, in the book of death. (B.Rosh Hashanah l6b) 
I strongly suspect that these Days of Awe are symbolic of the final days of the age during which repentance is yet possible – when mankind (and the church) will be given their last opportunity to repent before Yom Kippur. While we do not know what the the significance of the number of days is, a pertinent story in 1 Samuel is well worth reading.
When David and his men were on the run from King Saul, they asked from help from a “very great”, and obviously rich man called Naval, who is described as “churlish and evil” and a “worthless fellow”. In the past Naval had received protection from David’s men, but refuses to help David, who then leads four hundred men to war on Naval. A potential disaster is averted by Abigail, Naval’s wife who was not only beautiful, but “of good understanding”. She, unknown to her husband, packed large amounts of food on asses and took it to David’s camp where she asked David to spare her household, which he did. However when Abigail returns home she finds Naval very drunk and holding a feast in his house. So she says nothing until the next day when she tells him that she has made amends. Instead of admitting his error and repenting, Naval hardens his heart… Scripture telling us that “his heart died within him, and he became as a stone”. Ten days later God strikes him and he dies.
This is the story of a man who was given the opportunity to be a part of the coming kingdom of Israel under David; a type of the kingdom of God under Jesus. He refuses the offer and, although he does not know it, has ten days to change his mind and repent, which he does not do, with the result that he is slain at the end of the ten day period.
This is likely to be a foreshadowing of those people who, in the end times, will refuse to turn from their sin and seek God.
Rabbi Irving Greenberg writes that on Yom Kippur
“the ritual trial reaches its conclusion. Jews experience what a death sentence would mean by living as if dead for a day, giving up the fundamentals of dignified life. . . The people finally drop all their defenses and excuses and throw themselves on the mercy of the court, yet the same people never lose the conviction that they will be pardoned. This atonement is by divine grace; it is above and beyond the individual effort or merit.” 
The Feasts are in perfect chronological order, therefore Yom Kippur has to represent a day that follows Rosh HaShanah and the Ten Days of Awe. As discussed above, the symbolism of Rosh HaShanah seems glaringly obvious. They are the final opportunity anyone will get to repent before the doors finally close. And then comes Yom Kippur, the symbolism of which is found in the books of Hebrews and Revelation – passages that too many Christians have simply skimmed over.
The author of Hebrews both compared and contrasted the Old Testament ritual of the atonement with Christ’s redeeming sacrifice on the cross. He tells us how the imperfect observances on Yom Kippur (the Day of Atonement) are but a type, or a shadow of the perfect to come.
In the Old Testament, the high priest was barred from going behind the veil into the Most Holy Place of the temple but, on Yom Kippur, he was allowed into the presence of God to atone for the sins of the nation. He slaughtered both a bull as a sin offering for himself, and a goat as a sin offering for the people, then brought the blood of each behind the veil, and sprinkled it on and in front of the Mercy Seat. This ritual which took place every year pointed to a future event that had yet to occur. Jesus as our High Priest did not need to repeat the sacrifice but once, offering His own blood as a one time sacrifice for sin.
Again remembering that the details of this ceremony were laid out by God as a type of an event yet to take place, we turn to the ultimate sacrifice made by Jesus on Calvary. Just as the blood of the goat was shed, Jesus shed His blood for the atonement of sin YES! But Jesus’ blood has (in a sense) to be sprinkled on the Mercy Seat. To say that atonement is complete without this second part of the ritual is like saying Aaron atoned for his sins and the sins of the people just by slaughtering the animals outside the tent, then going off to have breakfast.
Because everything that Aaron was instructed to do was a type of something to come, we have to know that the second part of the ritual cannot be ignored. We know that Jesus shed His blood on Calvary, but when does (or did) the second part of the process actually happen? Hebrews 9:24-26 gives us a glimpse into the timing … Note the added emphasis
(24) For Christ did not enter a holy place made with hands, a mere copy of the true one, but into heaven itself, now to appear in the presence of God for us; (25) nor was it that He would offer Himself often, as the high priest enters the holy place year by year with blood that is not his own. (26) Otherwise, He would have needed to suffer often since the foundation of the world; but now once at the consummation of the ages He has been manifested to put away sin by the sacrifice of Himself. (Hebrews 9:24-26)
“Has been” is the perfect tense which, in English, always refers to actions completed at some time in the past but usually have some effect on the present. However, in the original Hebrew and Greek, the perfect tense is often used when the speaker intends to represent a futureaction as if it were already accomplished. The past tense is used to emphasize the certainty of a future event. Unfortunately, in the vast majority of the cases, the translators changed the perfect tense into the future tense, which gives us a false picture of what the author was saying.
In this case, the timing of the event is very specific. We are told exactly when Jesus puts away sin – – at the consummation of the ages. In other words, it is only at the end of the age that the Atonement is finally complete and Christians will be saved once and for all.
All of which ties in with the fact that the New Testament sometimes says that salvation is an accomplished reality, and at other times says it is still in the future. This seeming contradiction is not limited to salvation alone, but includes other topics… justification, redemption, glorification, and adoption. For example, Romans 8:15 says we have been adopted into God’s family
For you have not received a spirit of slavery leading to fear again, but you have received a spirit of adoption as sons by which we cry out, “Abba! Father!” (Romans 8:15 NASB)
But, just a few verses later we read that we are still awaiting adoption
And not only this, but also we ourselves, having the first fruits of the Spirit, even we ourselves groan within ourselves, waiting eagerly for our adoption as sons, the redemption of our body. (Romans 8:23 NASB)
Lets be very clear.. The Bible does not contradict itself on anything, much less on topics of crucial importance. So what is the answer? Have we been finally saved or not? Have we already been redeemed and justified or not? Have we already been adopted or are we ‘eagerly waiting’ to be?
The answer to all this questions is, exactly as the New Testament implies – BOTH. [For Details See The Two Phase Atonement
“Speak to the sons of Israel, saying, ‘On the fifteenth of this seventh month is the Feast of Booths for seven days to the Lord. ‘On the first day is a holy convocation; you shall do no laborious work of any kind. ‘For seven days you shall present an offering by fire to the Lord. On the eighth day you shall have a holy convocation and present an offering by fire to the Lord; it is an assembly. You shall do no laborious work. (Leviticus 23:34-36 NASB)
‘On exactly the fifteenth day of the seventh month, when you have gathered in the crops of the land, you shall celebrate the feast of the Lord for seven days, with a rest on the first day and a rest on the eighth day. ‘Now on the first day you shall take for yourselves the foliage of beautiful trees, palm branches and boughs of leafy trees and willows of the brook, and you shall rejoice before the Lord your God for seven days. ‘You shall thus celebrate it as a feast to the Lord for seven days in the year. It shall be a perpetual statute throughout your generations; you shall celebrate it in the seventh month. ‘You shall live in booths (Heb. sûkkâh) for seven days; all the native-born in Israel shall live in booths (Heb. sûkkâh), so that your generations may know that I had the sons of Israel live in booths (Heb. sûkkâh) when I brought them out from the land of Egypt. I am the Lord your God.'” (Leviticus 23:39-43 NASB)
The seventh and final Feast is the Feast of Booths (translated “Tabernacles” in the KJV). “Tabernacle” may not be the best translation because, in the Bible ,the word refers to God’s portable Sanctuary in the desert that was translated from the Hebrew mishkân. The shelters the Israelites lived in came from a different Hebrew word – sûkkâh, that simply means a temporary shelter made out of the branches of various trees and palm fronds.
Jonah made himself such a shelter (sûkkâh) so he could sit in the shade and see what was happening in Nineveh (Jonah 4:5 NASB)
and you shall rejoice in your feast, you and your son and your daughter and your male and female servants and the Levite and the stranger and the orphan and the widow who are in your towns. (Deuteronomy 16:14 NASB)
Then it will come about that any who are left of all the nations that went against Jerusalem will go up from year to year to worship the King, the Lord of hosts, and to celebrate the Feast of Booths. (Zechariah 14:16 NASB)
Note: Although they were both of post-Mosaic origin, there were two ceremonies performed on the Feast of Tabernacles – pouring out of water drawn from the pool of Siloam, and the illumination of the Temple that referred back to the water and the “pillar of light” provided during the wilderness wandering.
Chanukah celebrates the cleansing and rededication of the Temple to God, and was observed by Christ in theNew Testament. The Gospel of John tells us that
At that time the Feast of the Dedication took place at Jerusalem; it was winter, and Jesus was walking in the temple in the portico of Solomon. (John 10:22-23 NASB)
One of the first things you will probably notice when studying any chart of the Jewish Feasts is that they do not fall on specified dates according to the Gregorian calendar that is used in the Western world. The reason is that the Gregorian calendar (adopted in 1582 during the reign of Pope Gregory XIII) is a solar one that is related to the earth’s revolution around the sun. The Jews, in contrast, use a modified lunar calendar, or what might be called a lunar/solar calendar.
A year on the Gregorian calendar runs 365 days. But since it takes approximately 365 and a 1/4 days for the earth to make a complete circle around the sun, an extra day is added in February every four years, making a Leap Year of 366 days.
The Jewish calendar is based upon the movement of the moon around the earth. A full circle takes about 29 days. Thus, twelve of these lunar months add up to 354 days in a year. So, a solar year is 11 days longer than a lunar year.
If the Jews followed a strict lunar calendar, as the Muslims do, the feasts would migrate completely around the calendar (as the Muslim feast of Ramadan does.) But the Jews could not tolerate this since three of their feasts are related directly to the agricultural cycle. Therefore, they devised a method of modifying their lunar calendar to bring it in line with the solar year. They did this by adding an extra month of 29 days about every three years (7 times in 19 years). This month is called the intercalary month.
That’s the reason that the feast of Passover, for example, can occur in either March or April. The feast migrates backward on the Gregorian calendar for three years and then is propelled forward 29 days when the intercalary month is added. Passover always falls on Nisan 14 on the Jewish calendar, but that date moves around on the Gregorian calendar.
Another difference is that the Gregorian day begins at midnight, and runs until the next midnight. The Jewish day begins at sundown (approximately 6:00pm) and runs until the next day’s sundown. The Passover meal is celebrated at the beginning of Nisan 14, which would be in the evening.
 Dr. David R. Reagan. The Feasts of Israel A Study in Symbolic Prophecy
 As quoted in The Ten Days of Repentance By Rabbi Dr. Reuven Hammer.
 Rabbi Irving Greenberg (President of Jewish Life Network/Steinhardt Foundation) The Jewish Way. Living the Holidays (New York, 1988), pp. 207-208.