This is a word study on the phrase last days in the KJV.
The first occurance of the phrase is in the beginning of the chapter Genesis 49. The fact that it is in the intro of the chapter might suggest that the entire chapter is about it.
CHAP. XLIX. 1 Iacob calleth his sonnes to blesse them. 3 Their blessing in particular. 29 He chargeth them about his buriall. 33 He dieth. King James Version (1769) with Strongs Numbers and Morphology: Genesis Chapter 49  And Jacob called unto his sons, and said, Gather yourselves together, that I may tell you that which shall befall you in the last days.  Gather yourselves together, and hear, ye sons of Jacob; and hearken unto Israel your father.  Reuben, thou art my firstborn, my might, and the beginning of my strength, the excellency of dignity, and the excellency of power:  Unstable as water, thou shalt not excel; because thou wentest up to thy father’s bed; then defiledst thou it: he went up to my couch.  Simeon and Levi are brethren; instruments of cruelty are in their habitations.  O my soul, come not thou into their secret; unto their assembly, mine honour, be not thou united: for in their anger they slew a man, and in their selfwill they digged down a wall.  Cursed be their anger, for it was fierce; and their wrath, for it was cruel: I will divide them in Jacob, and scatter them in Israel.  Judah, thou art he whom thy brethren shall praise: thy hand shall be in the neck of thine enemies; thy father’s children shall bow down before thee.  Judah is a lion’s whelp: from the prey, my son, thou art gone up: he stooped down, he couched as a lion, and as an old lion; who shall rouse him up?  The sceptre shall not depart from Judah, nor a lawgiver from between his feet, until Shiloh come; and unto him shall the gathering of the people be.  Binding his foal unto the vine, and his ass’s colt unto the choice vine; he washed his garments in wine, and his clothes in the blood of grapes:  His eyes shall be red with wine, and his teeth white with milk.  Zebulun shall dwell at the haven of the sea; and he shall be for an haven of ships; and his border shall be unto Zidon.  Issachar is a strong ass couching down between two burdens:  And he saw that rest was good, and the land that it was pleasant; and bowed his shoulder to bear, and became a servant unto tribute.  Dan shall judge his people, as one of the tribes of Israel.  Dan shall be a serpent by the way, an adder in the path, that biteth the horse heels, so that his rider shall fall backward.  I have waited for thy salvation, O LORD.  Gad, a troop shall overcome him: but he shall overcome at the last.  Out of Asher his bread shall be fat, and he shall yield royal dainties.  Naphtali is a hind let loose: he giveth goodly words.  Joseph is a fruitful bough, even a fruitful bough by a well; whose branches run over the wall:  The archers have sorely grieved him, and shot at him, and hated him:  But his bow abode in strength, and the arms of his hands were made strong by the hands of the mighty God of Jacob; (from thence is the shepherd, the stone of Israel:)  Even by the God of thy father, who shall help thee; and by the Almighty, who shall bless thee with blessings of heaven above, blessings of the deep that lieth under, blessings of the breasts, and of the womb:  The blessings of thy father have prevailed above the blessings of my progenitors unto the utmost bound of the everlasting hills: they shall be on the head of Joseph, and on the crown of the head of him that was separate from his brethren.  Benjamin shall ravin as a wolf: in the morning he shall devour the prey, and at night he shall divide the spoil.  All these are the twelve tribes of Israel: and this is it that their father spake unto them, and blessed them; every one according to his blessing he blessed them.  And he charged them, and said unto them, I am to be gathered unto my people: bury me with my fathers in the cave that is in the field of Ephron the Hittite,  In the cave that is in the field of Machpelah, which is before Mamre, in the land of Canaan, which Abraham bought with the field of Ephron the Hittite for a possession of a buryingplace.  There they buried Abraham and Sarah his wife; there they buried Isaac and Rebekah his wife; and there I buried Leah.  The purchase of the field and of the cave that is therein was from the children of Heth.  And when Jacob had made an end of commanding his sons, he gathered up his feet into the bed, and yielded up the ghost, and was gathered unto his people.
The question I have here is if Jacob is talking about the descendants of the twelve tribes rather than the sons. In that case he could be talking about the current times. I dont know.
The last days are also mentioned in Isaiah 2.
CHAP. II. 1 Isaiah prophecieth the comming of Christs kingdome. 6 Wickednesse is the cause of Gods forsaking. 10 Hee exhorteth to feare, because of the powerfull effects of Gods Maiestie. King James Version (1769) with Strongs Numbers and Morphology: Isaiah Chapter 2  The word that Isaiah the son of Amoz saw concerning Judah and Jerusalem.  And it shall come to pass in the last days, that the mountain of the LORD’S house shall be established in the top of the mountains, and shall be exalted above the hills; and all nations shall flow unto it.  And many people shall go and say, Come ye, and let us go up to the mountain of the LORD, to the house of the God of Jacob; and he will teach us of his ways, and we will walk in his paths: for out of Zion shall go forth the law, and the word of the LORD from Jerusalem.  And he shall judge among the nations, and shall rebuke many people: and they shall beat their swords into plowshares, and their spears into pruninghooks: nation shall not lift up sword against nation, neither shall they learn war any more.  O house of Jacob, come ye, and let us walk in the light of the LORD.  Therefore thou hast forsaken thy people the house of Jacob, because they be replenished from the east, and are soothsayers like the Philistines, and they please themselves in the children of strangers.  Their land also is full of silver and gold, neither is there any end of their treasures; their land is also full of horses, neither is there any end of their chariots:  Their land also is full of idols; they worship the work of their own hands, that which their own fingers have made:  And the mean man boweth down, and the great man humbleth himself: therefore forgive them not.  Enter into the rock, and hide thee in the dust, for fear of the LORD, and for the glory of his majesty.  The lofty looks of man shall be humbled, and the haughtiness of men shall be bowed down, and the LORD alone shall be exalted in that day.  For the day of the LORD of hosts shall be upon every one that is proud and lofty, and upon every one that is lifted up; and he shall be brought low:  And upon all the cedars of Lebanon, that are high and lifted up, and upon all the oaks of Bashan,  And upon all the high mountains, and upon all the hills that are lifted up,  And upon every high tower, and upon every fenced wall,  And upon all the ships of Tarshish, and upon all pleasant pictures.  And the loftiness of man shall be bowed down, and the haughtiness of men shall be made low: and the LORD alone shall be exalted in that day.  And the idols he shall utterly abolish.  And they shall go into the holes of the rocks, and into the caves of the earth, for fear of the LORD, and for the glory of his majesty, when he ariseth to shake terribly the earth.  In that day a man shall cast his idols of silver, and his idols of gold, which they made each one for himself to worship, to the moles and to the bats;  To go into the clefts of the rocks, and into the tops of the ragged rocks, for fear of the LORD, and for the glory of his majesty, when he ariseth to shake terribly the earth.  Cease ye from man, whose breath is in his nostrils: for wherein is he to be accounted of?
In the second occurrence of the phrase the last days which is in Isaiah 2:2 we see that its mentioned in the chapter summary of Isaiah 2 that its about the coming of Christ kingdom. This seems to suggest that the last days are the entire new testament because Jesus says that the kingdom is within you and its about being born again.
The third occurance of the phrase last days is in Micah 4. Its in the first verse so the entire chapter might be about the last days.
CHAP. IV. 1 The Glory, 3 Peace, 8 Kingdome, 11 and Victorie of the Church. King James Version (1769) with Strongs Numbers and Morphology: Micah Chapter 4  But in the last days it shall come to pass, that the mountain of the house of the LORD shall be established in the top of the mountains, and it shall be exalted above the hills; and people shall flow unto it.  And many nations shall come, and say, Come, and let us go up to the mountain of the LORD, and to the house of the God of Jacob; and he will teach us of his ways, and we will walk in his paths: for the law shall go forth of Zion, and the word of the LORD from Jerusalem.  And he shall judge among many people, and rebuke strong nations afar off; and they shall beat their swords into plowshares, and their spears into pruninghooks: nation shall not lift up a sword against nation, neither shall they learn war any more.  But they shall sit every man under his vine and under his fig tree; and none shall make them afraid: for the mouth of the LORD of hosts hath spoken it.  For all people will walk every one in the name of his god, and we will walk in the name of the LORD our God for ever and ever.  In that day, saith the LORD, will I assemble her that halteth, and I will gather her that is driven out, and her that I have afflicted;  And I will make her that halted a remnant, and her that was cast far off a strong nation: and the LORD shall reign over them in mount Zion from henceforth, even for ever.  And thou, O tower of the flock, the strong hold of the daughter of Zion, unto thee shall it come, even the first dominion; the kingdom shall come to the daughter of Jerusalem.  Now why dost thou cry out aloud? is there no king in thee? is thy counsellor perished? for pangs have taken thee as a woman in travail.  Be in pain, and labour to bring forth, O daughter of Zion, like a woman in travail: for now shalt thou go forth out of the city, and thou shalt dwell in the field, and thou shalt go even to Babylon; there shalt thou be delivered; there the LORD shall redeem thee from the hand of thine enemies.  Now also many nations are gathered against thee, that say, Let her be defiled, and let our eye look upon Zion.  But they know not the thoughts of the LORD, neither understand they his counsel: for he shall gather them as the sheaves into the floor.  Arise and thresh, O daughter of Zion: for I will make thine horn iron, and I will make thy hoofs brass: and thou shalt beat in pieces many people: and I will consecrate their gain unto the LORD, and their substance unto the Lord of the whole earth.
In Micah 4 the phrase the last days is also mentioned. I think this people of all nations coming to Israel could be a reference to Christians who visit Israel during the period of the new testament.
So also here in acts 2:17 is the phrase the last days mentioned.
 But this is that which was spoken by the prophet Joel;  And it shall come to pass in the last days, saith God, I will pour out of my Spirit upon all flesh: and your sons and your daughters shall prophesy, and your young men shall see visions, and your old men shall dream dreams: (Acts 2:16-17 [KJV])
This seems to be a reference to the baptism in the Holy Ghost that was made possible after Jesus Christ ascension to heaven.
2 Timothy 3
The last days are mentioned in 2 timothy 3. These lasts days are called perilous.
CHAP. III. 1 Hee aduertiseth him of the times to come, 6 describeth the enemies of the trueth, 10 propoundeth vnto him his owne example, 16 and commendeth the holy Scriptures. King James Version (1769) with Strongs Numbers and Morphology: II Timothy Chapter 3  This know also, that in the last days perilous times shall come.  For men shall be lovers of their own selves, covetous, boasters, proud, blasphemers, disobedient to parents, unthankful, unholy,  Without natural affection, trucebreakers, false accusers, incontinent, fierce, despisers of those that are good,  Traitors, heady, highminded, lovers of pleasures more than lovers of God;  Having a form of godliness, but denying the power thereof: from such turn away.  For of this sort are they which creep into houses, and lead captive silly women laden with sins, led away with divers lusts,  Ever learning, and never able to come to the knowledge of the truth.  Now as Jannes and Jambres withstood Moses, so do these also resist the truth: men of corrupt minds, reprobate concerning the faith.  But they shall proceed no further: for their folly shall be manifest unto all men, as theirs also was.  But thou hast fully known my doctrine, manner of life, purpose, faith, longsuffering, charity, patience,  Persecutions, afflictions, which came unto me at Antioch, at Iconium, at Lystra; what persecutions I endured: but out of them all the Lord delivered me.  Yea, and all that will live godly in Christ Jesus shall suffer persecution.  But evil men and seducers shall wax worse and worse, deceiving, and being deceived.  But continue thou in the things which thou hast learned and hast been assured of, knowing of whom thou hast learned them;  And that from a child thou hast known the holy scriptures, which are able to make thee wise unto salvation through faith which is in Christ Jesus.  All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness:  That the man of God may be perfect, throughly furnished unto all good works.
So assuming that these lasts days then are basically the period after Jesus ascension until Jesus second coming. We are currently living in this period. And this can explain the terror that many christian experience in churches and that the martyrs experienced in the book of martyrs.
Hebrew 1 also mentions the phrase the last days.
CHAP. I. 1 Christ in these last times comming to vs from the Father, 4 is preferred aboue the Angels, both in Person and Office.  God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets,  Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds; (Hebrews 1:1-2 [KJV])
In Hebrew 1 it seems that the period the last days refer to the new testament period. Maybe the period from the beginning of the new testament until Jesus second coming.
The phrase the last days are also mentioned in James 5.
CHAP. V. 1 Wicked rich men are to feare Gods vengeance. 7 We ought to be patient in afflictions, after the example of the Prophets, and Iob: 12 to forbeare swearing, 13 to pray in aduersitie, to sing in prosperitie: 16 to acknowledge mutually our seueral faults, to pray one for another, 19 and to reduce a straying brother to the trueth. King James Version (1769) with Strongs Numbers and Morphology: James Chapter 5  Go to now, ye rich men, weep and howl for your miseries that shall come upon you.  Your riches are corrupted, and your garments are motheaten.  Your gold and silver is cankered; and the rust of them shall be a witness against you, and shall eat your flesh as it were fire. Ye have heaped treasure together for the last days.  Behold, the hire of the labourers who have reaped down your fields, which is of you kept back by fraud, crieth: and the cries of them which have reaped are entered into the ears of the Lord of sabaoth.  Ye have lived in pleasure on the earth, and been wanton; ye have nourished your hearts, as in a day of slaughter.  Ye have condemned and killed the just; and he doth not resist you.  Be patient therefore, brethren, unto the coming of the Lord. Behold, the husbandman waiteth for the precious fruit of the earth, and hath long patience for it, until he receive the early and latter rain.  Be ye also patient; stablish your hearts: for the coming of the Lord draweth nigh.  Grudge not one against another, brethren, lest ye be condemned: behold, the judge standeth before the door.  Take, my brethren, the prophets, who have spoken in the name of the Lord, for an example of suffering affliction, and of patience.  Behold, we count them happy which endure. Ye have heard of the patience of Job, and have seen the end of the Lord; that the Lord is very pitiful, and of tender mercy.  But above all things, my brethren, swear not, neither by heaven, neither by the earth, neither by any other oath: but let your yea be yea; and your nay, nay; lest ye fall into condemnation.  Is any among you afflicted? let him pray. Is any merry? let him sing psalms.  Is any sick among you? let him call for the elders of the church; and let them pray over him, anointing him with oil in the name of the Lord:  And the prayer of faith shall save the sick, and the Lord shall raise him up; and if he have committed sins, they shall be forgiven him.  Confess your faults one to another, and pray one for another, that ye may be healed. The effectual fervent prayer of a righteous man availeth much.  Elias was a man subject to like passions as we are, and he prayed earnestly that it might not rain: and it rained not on the earth by the space of three years and six months.  And he prayed again, and the heaven gave rain, and the earth brought forth her fruit.  Brethren, if any of you do err from the truth, and one convert him;  Let him know, that he which converteth the sinner from the error of his way shall save a soul from death, and shall hide a multitude of sins.
Here in James 5 it seems that the last days includes the final judgement. But its still part of the new testament period.
2 Peter 3
CHAP. III. Hee assureth them of the certaintie of Christes comming to Iudgement, against those scorners who dispute against it: 8 warning the godly for the long patience of God, to hasten their repentance. 10 He describeth also the manner how the world shall bee destroyed: 11 exhorting them from the expectation thereof, to all holinesse of life: 15 And againe, to thinke the patience of God to tend to their saluation, as Paul wrote to them in his Epistles. King James Version (1769) with Strongs Numbers and Morphology: II Peter Chapter 3  This second epistle, beloved, I now write unto you; in both which I stir up your pure minds by way of remembrance:  That ye may be mindful of the words which were spoken before by the holy prophets, and of the commandment of us the apostles of the Lord and Saviour:  Knowing this first, that there shall come in the last days scoffers, walking after their own lusts,  And saying, Where is the promise of his coming? for since the fathers fell asleep, all things continue as they were from the beginning of the creation.  For this they willingly are ignorant of, that by the word of God the heavens were of old, and the earth standing out of the water and in the water:  Whereby the world that then was, being overflowed with water, perished:  But the heavens and the earth, which are now, by the same word are kept in store, reserved unto fire against the day of judgment and perdition of ungodly men.  But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day.  The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance.  But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up.  Seeing then that all these things shall be dissolved, what manner of persons ought ye to be in all holy conversation and godliness,  Looking for and hasting unto the coming of the day of God, wherein the heavens being on fire shall be dissolved, and the elements shall melt with fervent heat?  Nevertheless we, according to his promise, look for new heavens and a new earth, wherein dwelleth righteousness.  Wherefore, beloved, seeing that ye look for such things, be diligent that ye may be found of him in peace, without spot, and blameless.  And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you;  As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.  Ye therefore, beloved, seeing ye know these things before, beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness.  But grow in grace, and in the knowledge of our Lord and Saviour Jesus Christ. To him be glory both now and for ever. Amen.
So in the last days there shall come scorners walking after their own lusts. Notice also in  that its mentioned that 1 day = 1000 years. So last days can be the last 2000 years which might end around 2056 with Jesus second coming (see Theological document).
That was the last mention of the phrase the last days in the king james bible.
The last days is maybe the period from the beginning of the new testament until Jesus second coming. Or it could maybe be the period from the day of pentacost until Jesus second coming.