The trumpets will announce the second coming of Jesus:
For the Lord himself will come down from heaven, with a loud command, with the voice of the archangel and with the trumpet call of God, and the dead in Christ will rise first. After that, we who are still alive and are left will be caught up together with them in the clouds to meet the Lord in the air. And so we will be with the Lord forever. (1.Thess 4,16-17) see also 1. Corinthians 15,51-52

THE DAYS OF TESHUVAH (Return or Repentance): On Elul 1(August or September - 6 months after Passover, which is the first month of Abib). This starts 30 days before the Feast of Trumpets. Feast of Trumpets is Tshri 1 (7th Month - September or October - in the 7th month. Remember Passover is in Abib, or Nissan, the first month) The days of Teshuvah, or days of Repentance, ends Tshri 10 - on Yom Kippur - Day of Atonement, (total of 40 days). The 40 days of Teshuvah, is a time of returning and repenting before The LORD. During those 40 days, and especially the last 10, and most particularly the LAST day of Yom Kippur, we prepare our heart by seeking forgiveness, through repentance. The last 10 days - the 10 days starting wth the Feast of Trumpets and ending with the Day of Atonement, or Yom Kippur, are known as the Days of Awe.
4. DAY OR FEAST OF TRUMPETS (Rosh HaShanah or Yom Teruach) Num 29:1; Lev 23:23-25: On Tishri 1. Rosh HaShanah means "head of the year." According to Jewish tradition, on this day the gates of heaven are opened, (Rev 3:7-11). Tradition has it as the anniversary of the creation of the world and the beginning of the Kingdom of HaShem (God), Adam and Eve were created, the flood waters dried up, Enoch was taken by the LORD; Sarah, Rachel, and Samuel were conceived, Joseph was freed from prison by Pharaoh, forced labor of Hebrews in Egypt ended, Job contracted leprosy, the start of sacrifices on the altar built by Ezra. According to Jewish tradition all of those events happened on Tishri 1. The Feast of Trumpets is celebrated by blowing trumpets (shofar) 100 times to announce the setting up of The LORD's eternal court.
The sounding of the shofar reminds us of the binding of Isaac by his father Abraham, and we too must be willing to make such sacrifices. On this day we reaffirm our acceptance of The LORD as our King, and He judges all of His human creatures on this day and decides on their fate in the coming year. It is the first month of the new civil year. These 10 days are called the Days of Awe or High Holy Days. This was also the time to bring all of your tithe (10th) for the poor, widows, orphans, and the Levite priest who have no inheritance. Over these 10 days the wheat will be brought in on the threshing floor and separated from the chaff. This 2-day feast comes AT A DAY AND HOUR NO MAN KNOWS and you are not required to go up to the temple on this day. a. This is the day set up to remember the blowing of trumpets when the great sign appeared in the heavens of the announcement of Yeshua’s birth (Lion of Judah), which the Chaldean astronomers had been watching, and waiting for, for over four hundred years, (Rev.12:1-2). b. Will be the announcement of Yeshua’s second coming and the Resurrection of the Saints, (IThess 4:16,17). c. Will be the end of Jacob’s trouble, (Jer 30:7). d. Will be the end of first Gog Magog War at the start of the millennial reign of King Yeshua.