There is the new theory by Luis Vega that the real Pentecost in Acts 2 is really 50 days after the Feast of Weeks because grapes in Israel could not be harvested and made into grape juice in May or June when the Feast of Weeks takes place which is also called Shavuot by the Jewish people and Pentecost by the writers of the New Testament. Some grapes in Israel can be harvested as early as mid to late July while others are harvested late August to early October. According to the Essenes' calendar the New Wine festival was always held on July 23, and so that is now being considered as the real Pentecost by some, and as a possible Rapture date.
However, if you read the article below, it will tell you how the new wine (grape juice) could be preserved so that it could be drank during the entire year. In fact, Jesus drank grape juice at the Last Supper according to Mark 14:25 when He called it the fruit of the vine. Because He drank it at the Last Supper in March or April (?), there is no reason why grape juice couldn't be drank in May or June when the Feast of Weeks (Shavuot or Pentecost) takes place. According to Mark 14:23-25 it says, "And he took the cup, and when he had given thanks, he gave it to them: and they all drank of it. And he said unto them, This is my blood of the new testament, which is shed for many. Verily I say unto you, I will drink no more of the fruit of the vine, until that day that I drink it new in the kingdom of God." Now please read the article below:
"It is often supposed that in Bible times, grape juice inevitably fermented if kept for any length of time...
and that therefore whenever the Bible mentions “wine,” it is referring to the alcoholic beverage commonly called “wine” today. However, ancient civilizations had several ways of preventing fruit and fruit juices from fermentation, and thus were able to have non-alcoholic wine (grape juice) throughout the year."
Preventing fermentation
1) "One method involved boiling the juice and reducing it to a syrup that could later be diluted with water."
2) "Another was to boil the juice with minimum evaporation and then immediately seal it with beeswax in airtight jars."
3) "Drying the fruit in the sun and then reconstituting it with water, adding sulfur to the fruit juice, or filtering the juice to extract the gluten were also methods that would prevent the juice from fermenting."
"These means of preservation were known to the ancients, who also practiced boiling fermented juice to eliminate the alcohol."
Unfermented wine in ancient literature
"Referring to reconstituting grape syrup to make grape juice, Aristotle, who was born around 384 b.c., wrote “The wine of Arcadia was so thick that it was necessary to scrape it from the skin bottles in which it was contained and to dissolve the scrapings in water” (quoted in Nott’s Lectures on Biblical Temperance, p. 80). The poet Horace, born in 65 b.c., wrote, “There is no wine sweeter to drink than that of Lesbos; it was like nectar . . . and would not produce intoxication.”
“The Mishna [a collection of oral Jewish traditions] states that the Jews were in the habit of drinking boiled wine” (Kitto’s Cyclopedia of Biblical Literature, vol. 2, p. 447). Naturally, this wine would be entirely free of alcohol as a result of the boiling, if not also from the manner of preservation."
Additional information
"In his commentary on the Gospel of John, Albert Barnes wrote, “The wine of Judea was the pure juice of the grape, without any mixture of alcohol. It was the common drink of the people and did not produce intoxication.” And Adam Clarke, commenting on Genesis 40:11, wrote, “From this we find that wine anciently was the mere expressed juice of the grape without fermentation. The saky, or cupbearer, took the bunch [of grapes], pressed the juice into the cup, and instantly delivered it into the hands of his master. This was anciently the yayin [wine] of the Hebrews, the oinos [wine] of the Greeks, and the mustum [wine] of the ancient Latins.” Clarke’s comments agree with the Scripture that declares “As the new wine is found in the cluster, and one says, ‘Do not destroy it, for a blessing is in it’ ” (Isaiah 65:8, NKJV). FULL STORY at above link.So the disciples in the upper room in Acts 2 could have drank the new wine of grape juice on the Feast of Weeks (Pentecost or Shavuot) 50 days after the Feast of First Fruits because grape juice can be preserved all year round. And the other men present at Pentecost heard the disciples speak with other tongues, and according to Acts 2:13, these other men present there said, These men (disciples) are full of new wine.The commentary at ηδυς | Abarim Publications Theological Dictionary (New Testament Greek) says the following about the new wine in Acts 2:13:"The noun γλευκος (gleukos), which describes a kind of unfermented sweet grape juice, the same as mustum or mustus or dulce in Latin. Our noun occurs in Acts 2:13 only, in the curious report of the men who witness the divinely inspired disciples speak in multiple languages simultaneously:On Acts 2:13"If the scoffers had intended to explain the disciples' sudden linguistic talents as the effects of an excess of alcohol (as some commentators curiously maintain), the scoffers would have used words like οινος (oinos), wine, and μεθυ (methu), liquor. Instead, they declared that the disciples were full of γλευκος (gleukos), which was a famously unfermented kind of grape juice: alcohol-free wine, if you will. When Peter subsequently stated that they were not drunk (μεθυω, methuo), he essentially declared that their actions did not stem from the abundance of ingress of any kind, alcoholic or otherwise."Please don't forget that the Israelites were commanded to go up to Jerusalem 3 times during the year by the Lord God which was for the Feast of the Passover, the Feast of Weeks also called Shavuot or Pentecost, and for the Feast of Tabernacles also called Sukkot or the Feast of the Ingathering, and nowhere in the Old Testament does it say that they were commanded to go up to Jerusalem at the New Wine festival which took place 50 days after the Feast of Weeks (Pentecost).