The Feat of Trumpets
Currently we are in the seventh biblical month and it is the first day begins after sunset tonight which is when Elohim said to celebrate the Feast of Trumpets.
Lev 23:23 And the LORD spake unto Moses, saying,
Lev 23:24 Speak unto the children of Israel, saying, In the seventh month, in the first day of the month, shall ye have a sabbath, a memorial of blowing of trumpets, an holy convocation.
Lev 23:25 Ye shall do no servile work therein: but ye shall offer an offering made by fire unto the LORD.
We need to understand the purpose of celestial the bodies, The Sun the Moon and the stars because we want to be in the right place at the right time according to his instructions. We must identify properly the way Elohim told us to see the Days, and nights and to show us signs and seasons and years. In America we follow the Gregorian (Pope Gregory) calendar which breaks from the Biblical method that Elohim put in his design.
Gen 1:14 And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:
Gen 1:15 And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so.
Gen 1:16 And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also.
Gen 1:17 And God set them in the firmament of the heaven to give light upon the earth,
Gen 1:18 And to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good.
Gen 1:19 And the evening and the morning were the fourth day.

The biblical day begins in the evening after sundown with that full day being complete at sundown the next day.
A proof of the biblical day beginning in the evening beyond Genesis 1:19 can be observed when they were rushing to bury Christ. The Sabbath was about to begin in the evening and they rushed his burial so that they would not be guilty of working on the Sabbath.
Luk 23:50 And, behold, there was a man named Joseph, a counsellor; and he was a good man, and a just:
Luk 23:51 (The same had not consented to the counsel and deed of them;) he was of Arimathaea, a city of the Jews: who also himself waited for the kingdom of God.
Luk 23:52 This man went unto Pilate, and begged the body of Jesus.
Luk 23:53 And he took it down, and wrapped it in linen, and laid it in a sepulchre that was hewn in stone, wherein never man before was laid.
Luk 23:54 And that day was the preparation, and the sabbath drew on.
Luk 23:55 And the women also, which came with him from Galilee, followed after, and beheld the sepulchre, and how his body was laid.
Luk 23:56 And they returned, and prepared spices and ointments; and rested the sabbath day according to the commandment.

Psalm 104:19 He appointed the moon for seasons: the sun knoweth his going down.
In the Hebrew calendar all months are 30 days according to the book of Enoch.
And on the first day as the thirtieth day closes she (the moon) becomes visible. Note that she is very hard to see because she is near the sun but in the evening as the sun goes down you can see her sliver of light in the west.
Enoch Chapter 73 verse 4 and 5.
4. And thus she rises. And her first phase in the east comes forth on the thirtieth morning: and on that day she becomes visible, and constitutes for you the first phase of the moon on the thirtieth day together with the sun in the portal where the sun rises.
5. And the one half of her goes forth by a seventh part, and her whole cir--Donkey--ference is empty, without light, with the exception of one-seventh part of it, (and) the 6 fourteenth part of her light.

The mid month full moon happens on the 14th day
Enoch chapter 78 verses 6-7
6. And when the Moon rises, it appears in the sky, and has a half of a seventh part of light, and on the fourteenth day it makes all its light full.
7. And fifteen parts of light are transferred to it, until on the fifteenth day its light is full, according to the sign of the year, and amounts to fifteen parts. And the Moon comes into being by halves of a seventh part.

Note: verse 12 doubles down declaring the first day of the month with the sliver of light rising on the moon.
12. And on the first day it is called the New Moon, for on that, daylight rises on it.

Note verse 14 shows that the last day of the biblical month is when there is no light from the moon.
14. And on the side on which the light of the Moon appears, there again it wanes, until all its light disappears, and the days of the Moon end and its disc remains empty without light.
The feast of Trumpets
Lev 23:23 And the LORD spake unto Moses, saying,
Lev 23:24 Speak unto the children of Israel, saying, In the seventh month, in the first day of the month, shall ye have a sabbath, a memorial of blowing of trumpets, an holy convocation.
Lev 23:25 Ye shall do no servile work therein: but ye shall offer an offering made by fire unto the LORD.