Leviticus 23:23-25.
The Feast of Trumpets.
:23 Then the LORD spoke to Moses, saying,
:24 "Speak to the children of Israel, saying: "In the seventh month, on the first day of the month, you shall have a sabbath-rest, a memorial of blowing of trumpets, a holy convocation.
:25 You shall do no customary work on it; and you shall offer an offering made by fire to the LORD."

The seventh Hebrew month is called Tishri which corresponds to September/October.
Tishri is also the first month on the Jewish civil calendar.

The following are all the different names used to describe the first day of the seventh month in the Jewish calendar:

Rosh HaShanah - New Year.
Yom Teruah - The Day of the Awakening Blast or The Day of the Awakening Shout.
Feast of Trumpets - Yom HaDin - Day of Judgment.
Yom HaZikkaron - Day of Remembrance.
Yom HaKeseh - Day of the Hiding or Hidden Day.

This feast is celebrated over two days to make sure that everyone marked the new moon on the same day. To make sure nobody missed it, two days were appointed.

Tradition states that this is the birth day of Adam (could the second Adam, Jesus, have been born on the same day?).

Yom Teruah can be interpreted to mean "The Day of the Awakening Shout."

1 Thessalonians 4:15-17
:15 For this we say to you by the word of the Lord, that we who are alive and remain until the coming of the Lord will by no means precede those who are asleep.
:16 For the Lord Himself will descend from heaven with a shout, with the voice of an archangel, and with the trumpet of God. And the dead in Christ will rise first.
:17 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. 18Therefore comfort one another with these words.

There are three trumpets that have a name:
The first trump.
The last trump.
The great trump.
Each has a specific day in the year: first trump is associated with Pentecost, last trump is associated with Rosh HaShanah and the great trump is associated with Yom Kippur.

1 Corinthians 15:52
"in a moment, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, and the dead will be raised incorruptible, and we shall be changed".

When the Shofar is blown on Rosh HaShana, three different types of noises are sounded.
The first is a 'teki'ah.' - This sound is one long continuous burst.
The second sound is called a 'shevarim.' - It consists of three shorter blasts.
The third sound is the 'teruah.' - The teruah is a set of nine short bursts of sound, a staccato blast.

This is the only day in the whole year that was referred to as the hidden day or the day that no man knows.

Matthew 24:36
No One Knows the Day or Hour
"But of that day and hour no one knows, not even the angels of heaven, but My Father only.

The trumpet is blown throughout Elul (the month before Rosh HaShanah) except for the last day. The trumpet is silent because much about Rosh HaShanah is concealed and shrouded in mystery and Satan is not to be given notice about the arrival of Rosh HaShanah.

One custom for this day is to avoid sleeping, especially during evening and morning hours.

On this day you are to bow, bend the knee and prostrate yourselves in awe and thanksgiving. This is unusual as Jewish custom does not include many instances of kneeling or prostration.

Revelation 3:5
"He who overcomes shall be clothed in white garments, and I will not blot out his name from the Book of Life; but I will confess his name before My Father and before His angels".

The customary greeting for Rosh HaShanah is--"Shanah tovah tikatevu" ("May you be inscribed [in the book of life] for a good year") and on Yom Kippur--"Chatimah tovah" ("[May you have] a good sealing [of your destiny in the book of life]").

Tradition states that on Rosh HaShanah "God opens the heavenly books and judges the people according to their works, writing in them who will die and what kind of life the living will enjoy during the coming year. The Ten Days of Penitence (Rosh HaShanah through Yom Kippur) are thought of as offering an opportunity for repentance that will influence God to change these fates for the better. But on Yom Kippur these fates are fixed or 'sealed.'"

"Three books opened:
- that of life, for those whose works had been good;
- another of death, for those who had been thoroughly evil;
- intermediate, for those whose case was to be decided on the Day of Atonement (ten days after Rosh HaShanah on Yom Kippur), the delay being granted for repentance, or otherwise, after which their names would be finally entered, either in the book of life, or in that of death."

Revelation 20:12
"And I saw the dead, small and great, standing before God, and books were opened. And another book was opened, which is the Book of Life. And the dead were judged according to their works, by the things which were written in the books".