Below I put 3 important NT verses about the firstfruits.  THE Bible says we have the firstfruits of the Spirit, and we are a kind of firstfruits of his creatures.  I believe Rev 14:4 is about the church which says emphatically the redeemed are the firstfruits.

I also put an article on the firstfruits below.  Pentecost was the first day they could be brought in and they were identified by tying a reed around them-they were “marked” or “sealed”.

Revelations says you either have the mark of God or the mark of the devil.

We have been sealed by the Holy Spirit until the day of redemption-EPH 4:30

So if the church is the firstfruits, they cant be brought in until Pentecost and in temple times they could be brought in as late as Hannukah.  That would seem to indicate that the rapture has to happen between Pentecost and Hannukah.  God has told the end from the beginning and whatever has been is what will be.

Rom 8:23 And not only they, but ourselves also, which have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption, to wit, the redemption of our body.

Jam 1:18 Of his own will begat he us with the word of truth, that we should be a kind of firstfruits of his creatures.

Rev 14:4 These are they which were not defiled with women; for they are virgins. These are they which follow the Lamb whithersoever he goeth. These were redeemed from among men, being the firstfruits unto God and to the Lamb.

FROM WIKIPEDIA ABOUT FIRSTFRUITS

Shavuot was also the first day on which individuals could bring the Bikkurim (first fruits) to the Temple in Jerusalem (Mishnah Bikkurim 1:3). The Bikkurim were brought from the Seven Species for which the Land of Israel is praised: wheat, barley, grapes, figs, pomegranates, olives, and dates (Deut. 8:8).

In the largely agrarian society of ancient Israel, Jewish farmers would tie a reed around the first ripening fruits from each of these species in their fields. At the time of harvest, the fruits identified by the reed would be cut and placed in baskets woven of gold and silver. The baskets would then be loaded on oxen whose horns were gilded and laced with garlands of flowers, and who were led in a grand procession to Jerusalem. As the farmer and his entourage passed through cities and towns, they would be accompanied by music and parades.[9]

Will S