I will give you my view. You can research it yourself and make up your own mind.
On the topic of Does “New” Moon mean “Full” Moon.
Some read Psalms 81:3 and conclude that the new moon is a holy feast day and that the new Moon is the full moon and not the first light of the moon.
The KJV reads:
“Blow the trumpet in the NEw moon, in the time appointed, on our solemn feast day”.
Time appointed means “to plump, ie.e fill up hollows”. This appointed time is a full moon filled with light. Does this mean that the new moon is the full moon?
I believe the KJV and some other translations add to the confusion by not translating Psalm 81:3 precisely.
Other translations clear up the confusion showing two distinctly separate observances in this verse.
The NIV reads:
“Sound the ram’s horn at the New Moon, and when the moon is full, at the day of our feast.”
Psalm 81:3 is speaking if a new moon as well as another appointed time that comes at the full moon. During each of these separate times the trumpet was to sound – hence why we have both appointed times showing in the same verse.
The Biblica Hebraica Stuttgartensia version reads:
“Blow the trumpet at the new moon, and in the fullness of our festival day.:
The interlinear NIV reads
“Sound the ram’s horn at the New Moon, and when the moon is full, on the day of our feast.”
The complete Jewish Bible reads:
“Sound the shofar at Rosh-Hodesh (New Moon), and at the full moon for the pilgrim feast.”
The Psalms for Today: A New Translation from the Hebrew into Current English translates the verse: “Sound the trumpet at the new moon, and at the day of our festival, when the moon is full.”
These Hebrew based translations show the new moon is different to the full moon and different to the feast days. They show that the new moon and the full moon are not synonymous.
The Hebrew word levanah meaning white, occurs three times in the Hebrew text and poetically refers to the white brilliance of the full moon (see Song of Solomon 6:10; Isa. 24:23; 30:26). And the Hebrew word kehseh, meaning fullness, is twice translated full moon (Ps. 81:3; Prov. 7:20). Chodesh, on the other hand, refers to the new moon and is never used for full moon.
YHWH gives us signs in the sun, moon and stars. I note that the solar eclipse indicated the start of the new year. I note that the blood moons fall upon the Passover and Feast of Trumpets.
If YHWH gave us the sun moon and stars to be signs, I believe he is providing us with these signs to assist us to know when His appointed times are throughout the year.
These days I try not to reply on man made tradition, but look at what He has provided us. But once one has determined these things from His signs, it reinforces other things we see.
Vine’s says, “Chodesh means ‘new moon,’ ‘month.’ The word refers to the day on which the crescent reappears.”
The Theological Wordbook of the Old Testament says of (c)hodesh, “Although this word properly means ‘new moon,’ it is commonly used as an equivalent to our word ‘month’ because the month began when the thin crescent of the new moon was first visible at sunset.”
The International Standard Bible Encyclopedia says hodhesh (chodesh) means “‘new,’ ‘fresh.’ As the Hebrews reckoned their months from the actual first appearance of the young crescent, hodhesh is most frequently translated ‘month’ ” (Vol. 1, p. 303).
Then we see things like this which to me serves as a triple confirmation.
The verb form of (c)hodesh is hadash, a primitive root meaning to rebuild, renew, repair, refresh. This gives us additional proof as to what constitutes a new moon. A full moon is not in the rebuilding or renewing stage. It is already rebuilt, complete, and as full as it will get before waning back down to nothing, where it starts to re-grow from complete blackness once more.
The New Brown Driver Briggs Gesenius says chodesh is rooted in the meaning of conceal, as in “to conceal behind a curtain.” A full moon is anything but concealed. A crescent, on the other hand, is nearly all concealed by a curtain of darkness except for just a curved sliver of light along the right edge.
In the end the decision is up to the individual. It is not for me to push upon anyone, but I am happy to show you why I believe what I do.