Matthew 12:38 Then certain of the scribes and of the Pharisees answered, saying, Master, we would see a sign from Thee.
39 But He answered and said unto them, An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas:
40 For as Jonas was three days and three nights in the whale’s belly; so shall the Son of man be three days and three nights in the heart of the Earth.
41 The men of Nineveh shall rise in judgment with this generation, and shall condemn it: because they repented at the preaching of Jonas; and, behold, a greater than Jonas is here.

The sign of the prophet Jonah involves more than Messiah's 3 days and 3 nights in the heart of the Earth at His crucifixion. It involves the men of Nineveh condemning YAHUSHUA's generation, because the men of Nineveh repented at Jonah's preaching, but YAHUSHUA's generation did not repent at His preaching.

From chapter 3 verse 2 above, we see that Jonah was to preach the preaching that YaHuWaH gave him. Verse 4 above tells us Jonah's preaching was 'Yet forty days, and Nineveh will be overthrown'. That was YaHuWaH 's message to Nineveh.

The People of Nineveh Respond to YaHuWaH 's Message with Repentance

Jonah 3:5 So the people of Nineveh believed Elohim, and proclaimed a fast, and put on sackcloth, from the greatest of them even to the least of them.
6 For word came unto the king of Nineveh, and he arose from his throne, and he laid his robe from him, and covered him with sackcloth, and sat in ashes.
7 And he caused it to be proclaimed and published through Nineveh by the decree of the king and his nobles, saying, Let neither man nor beast, herd nor flock, taste any thing: let them not feed, nor drink water:
8 But let man and beast be covered with sackcloth, and cry mightily unto Elohim: yea, let them turn every one from his evil way, and from the violence that is in their hands.
9 Who can tell if Elohim will turn and repent, and turn away from his fierce anger, that we perish not?
10 And Elohim saw their works, that they turned from their evil way; and Elohim repented of the evil, that He had said that He would do unto them; and He did it not.

The Timing of Messiah's Resurrection

Messiah was probably born sometime between 7 BC and 3 BC, with John the Baptist being born about 6 months earlier than Messiah.

Hebrew priests entered into ministry service at the age of 30 years. John Baptist probably would have entered his ministry at age 30 about 6 months ahead of YAHUSHUA Messiah because John was been born about 6 months before Messiah. The birth sequence would ensure that 30 years later John would enter ministry ahead of Messiah in order to prepare the way for Messiah's coming.

This means that YAHUSHUA's ministry probably began between 24 AD (if Messiah was born in 7 BC) and 28 AD (if Messiah was born in 3 BC). (When counting from AD to BC subtract an extra year. There is no year '0', but a transition from 1 AD to 1 BC.) This also means that the crucifixion would probably have occurred sometime between 26 AD and 32 AD.

Jerusalem Destroyed 40 Years after Messiah's Resurrection

The people of Jerusalem didn't repent at Messiah's preaching. As a result, Jerusalem was destroyed in 70 AD. (30 AD + 40 years)

This is the first completion of the sign of the prophet Jonah. "Yet forty days, and Nineveh shall be overthrown". The people of Nineveh repented and were spared destruction. The people of Jerusalem didn't repent and their city was destroyed, not 40 days later but 40 years later. We now find ourselves living 40 jubilees later.

The Present Day, 40 Jubilees after the Resurrection

We find our present world again at the end of a biblically significant period of time. 40 Jubilees have elapsed since the resurrection of Messiah. 40 X 49 = 1960 + 30(AD) = 1990 AD, approximately the end of 40 jubilees.

Summary

Nineveh was spared because of the repentance of it's people upon hearing Jonah's message.

The people of Jerusalem didn't repent at the preaching of YAHUSHUA Messiah and Jerusalem was destroyed 40 years later.

The destruction of Jerusalem and it's Temple in 70 AD was a horrific example to the world of YaHuWaH 's judgment on unrepentant people. According to Josephus, 1,100,000 people were slaughtered.

The judgment of YaHuWaH is coming upon us. World wide repentance would spare us, but YAHUSHUA Messiah indicates in Matthew 24:39 that repentance will not occur on a major scale before His coming.

Matthew 24:37 But as the days of Noah were, so shall also the coming of the Son of man be.
38 For as in the days that were before the flood they were eating and drinking, marrying and giving in marriage, until the day that Noah entered into the ark,
39 And knew not until the flood came, and took them all away; so shall also the coming of the Son of man be.

Please prepare yourself and your loved ones to weather the storms of judgment about to strike the Earth. As with Noah and Lot, YaHuWaH will shelter His own in the time of trouble.

Luke 21:28 And when these things begin to come to pass, then look up, and lift up your heads; for your redemption draweth nigh.