* The Jewish calendar was based on observation but after Rome destroyed the temple in 70 AD, the Sanhedren adopted a 19-year calculated cycle. Since time is set by the sun, moon and stars, a few new months start before the observation of the new cresent moon and some leap months should be added earlier delaying the new year. See 2022 - Jewish Calendar. Jewish days begin at sunset.

He [Pilate] went out again unto the Jews, and said unto them, I find in him no fault at all. But you have a custom, that I should release unto you one at the passover: will you [want] that I release unto you the King of the Jews (John 18:38-39)?

Purge out therefore the old leaven, that you may be a new lump, as you are unleavened. For even Christ our passover is sacrificed for us (1 Corinthians 5:7).

3. Firstfruits - Resurrection - 16th of Nisan or day after regular Sabbath

Now is Christ risen from the dead, and become the firstfruits of them that slept. But every man in his own order: Christ the firstfruits; afterward they that are Christ's at his coming (1 Corinthians 15:20, 23).

4. Weeks/Pentecost - Law & Holy Spirit Given - 6th of Sivan or fifty days after regular Sabbath

The Comforter, which is the Holy Spirit, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you (John 14:26).

Since the death, burial and resurrection of Jesus Christ and the giving of the Holy Spirit were fulfilled on specific feast days in the spring for redemption, then the Rapture, Second Coming and reign of Jesus Christ will be fulfilled on specific feast days in the fall for return. To calculate Firstfruits and Pentecost, Pharisees count from the High Sabbath but Sadducees count from the regular Sabbath.

5. Trumpets - Rapture - 1st of Tishri

In a moment, in the twinkling of an eye, at the last trump [of a hundred]: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed (1 Corinthians 15:52).

Trumpets occurs in the fall  but no one knows what day until the new crescent moon is observed by two witnesses. They testify before the Sanhedrin who proclaims the new year. On Rosh Hashanah, the shofar (rams horn trumpet) is blown one hundred times. The last trump is called the Tekiah Gedolah.

I will pour upon the house of David, and upon the inhabitants of Jerusalem, the spirit of grace and of supplications: and they shall look upon me whom they have pierced, and they shall mourn for him, as one mourns for his only son, and shall be in bitterness for him, as one that is in bitterness for his firstborn (Zechariah 12:10).

It shall come to pass, that every one that is left of all nations which came against Jerusalem shall go up from year to year to worship the King, the Lord of hosts, and keep the feast of tabernacles (Zechariah 14:16).
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Note: Compare world events to time (Jewish major/minor holy days). The Bible verifies history and prophecy. From Columbus to the Tribulation, there are at least 130 events that match including World Wars, Cold War, Iraq Wars, End Wars.
Passover: Abraham, Exodus, Crucifixion (Exodus 12:40-41, Galatians 3:14, 17)
Golden Calf: Babylonians, Romans breach the walls of Jerusalem, Independence Day

US Presidents on Jewish Holy Days

9th of Av - Kadesh Barnea Rebellion - Israeli Judgment Day

From Mt. Sinai to Armageddon, this day has been fulfilled throughout the years.

Caleb stilled the people before Moses, and said, Let us go up at once, and possess it [the Promised Land]; for we are well able to overcome it. But the men that went up with him said, We are not able to go up against the people; for they are stronger than we (Numbers 13:30-31, 32, 33).

The first 9th of Av (July/August) was Israel's rebellion at Kadesh Barnea. A year after God's miraculous deliverance from Egypt, twelve spies explored Canaan forty days. The Hebrews had a choice to follow God's plan and take the Promised Land or believe the evil report and rebel against God. Because of their lack of faith, ten spies rebelled against God, discouraged the people and they all wander in the wilderness forty years.

Observed as a fast day, it has become a day of God's judgment against Israel and the world.
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9th of Av in Ancient History

In 2012, the Mayan calendar receives plenty of attention for predicting "the end of the world". However, the Jewish calendar is the key to understand God's plan to transition from human's rule to God. The holy days God gave to Moses and Israel is fulfilled in the seven day of Jesus Christ's redemption and return. Then the major and minor feasts and fast days are fulfilled in major events of the last one hundred years.

There is an amazing correlation between seven Jewish holy days/appointed times (Passover, Unleavened Bread, Firstfruits, Weeks/Pentecost, Trumpets, Atonement, Tabernacles) with minor Jewish days and seven trumpets wars of the 20th and 21st century (World War I, World War 2, Cold War, Iraq War I, Iraq War II, World War III, Armageddon). Major Bible prophecy is fulfilled before the Tribulation.

These are the feasts of the Lord, even holy convocations, which you shall proclaim in their seasons (Leviticus 23:4).