The following two versus pertain to the rapture, and not to the second coming of Christ. The rapture and the second coming of Christ are two separate events.

Please take special note of the words "trumpet" and "shout" in the next four paragraphs...

1 Corinthians 15: 52 - It will happen in a moment, in the blink of an eye, when the last trumpet is blown. For when the trumpet sounds, those who have died will be raised to live forever. And we who are living will also be transformed.

1 Thessalonians 4:16-17 – For the Lord Himself will descend from Heaven with a shout with the voice of the archangel, and with the trumpet of God; and the dead in Christ shall rise first. Then we who are alive and remain shall be caught up together with them in the clouds to meet the Lord in the air, and thus we shall always be with the Lord.”

(The following is an excerpt, taken from secular website, Wikipedia.com…)
"Jubilee" -- Etymology: The Septuagint rendered the Hebrew yovel as "a trumpet-blast of liberty" (ἀφέσεως σημασία afeseos semasia), and the Vulgate by Latin iobeleus. Traditionally, it was thought that the English term Jubilee derives from the Hebrew term yobel (via Latin Jubilaeus), which in turn derives from yobhel, meaning ram; the Jubilee year was announced by a blast on a shofar, an instrument made from a ram's horn, during that year's Yom Kippur.

An alternative etymology notes that the Latin verb iūbilō, "shout for joy," predates the Vulgate, and proposes that instead the Latin jubilo (meaning shout), as well as Middle Irish ilach (victory cry), New English yowl, and Ancient Greek iuzo (ἰύζω: shout), derived from the Proto-Indo-European root *yu- (shout for joy). In this case the Hebrew term for "jubilee" is a borrowing from neighboring Indo-European languages, rather than deriving from another Hebrew word.

SEPTEMBER 2015:
September 13 ,2015
• The end of the Shemita year (i.e., end of the Sabbath (sabbatical) or 7th year)
• Elul 29

September 14-15, 2015
• Rosh Hashanah begins at sundown on Sep 14 and ends at sundown on Sep 15. Rosh Hashanah, comes from the Hebrew words, Rosh Hashinui—the beginning of change.
• Beginning of the new Shemita 7-year cycle

September 23, 2015
• Day of Atonement
• The Jewish Jubilee (occurring every 50 years)
a) This will be the 40th Jubilee since Jesus’ death
b) This will be the 70th Jubilee since Moses (when Jubilees began)
c) This will be the 120th Jubilee since the beginning of time (120 x 50 years = 6000 years). In other words, according to the Jewish calendar, it is the completion of 6000 years, or the 6th millennium, which also marks the beginning of the 7th millennium. Perhaps the 7th millennium is the millennium of peace that Jesus will reign over.

“But do not let this one fact escape your notice, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day.” – 2 Peter 3:8. You’ve probably heard that verse before, but did you know that it is given in the context of the last days? If a thousand years is but a day, and we’re coming up to the beginning of the 7th millennium, or in God’s eyes, 7th day, this would be the day or millennium of rest… of peace, such as described in Revelation, which occurs after the rapture and tribulation.

September 28, 2015
• Jewish holiday, Sukkot (i.e. Feast of Tabernacles/Booths) – Lasts 7 days
• The fourth and final Blood Moon, which will also be a “supermoon” and the end of the tetrad, and will be visible in Jerusalem. Lunar eclipses, or “Blood Moons”, are not visible to all, all over the earth.

Summation:
Noting that the number 7 in biblical terms is a representation of wholeness, or completeness, perhaps the 70th Jubilee, is the last Jubilee, or the last the trumpet will be blown for this celebration – the last trump, and therefore the time appointed for the rapture.

Whether it is or isn’t, it certainly seems a very plausible theory. And what we can know for sure is something is going to happen in September 2015 that will affect and possibly change the whole world as we know it.