YHVH works in the circular not the linear and if one wants to understand the pattern He devised from Scripture, then he must lose his Babylonian mindset and start also think in the circular and not linear.
This pattern shows not only that YHVH does not change (Mal.3,6) but it also shows His eternal existence in the circular mode, never ending, just simply coming back to the beginning of the same pattern that He exists in. Since YHVH does not change if you can find the pattern, then simply follow it on each course of the calendar during the year.
YHVH works in the circular not the linear and the month revolves around the geometrical sphere of the moon as a perfect circle.
When you see a quarter moon it is ¼ of the month. When you see a full moon it is half month, when you see a waning quarter it is ¾ over and when the moon is dark and resetting it is new moon. YHVH also forbids us to look up at the sun and the moon and stars and to worship them
And lest thou lift up thine eyes unto heaven, and when thou seest the sun, and the moon, and the stars, even all the host of heaven, shouldest be driven to worship them, and serve them, which the Lord thy G-d hath divided unto all nations under the whole heaven. Deu.4:19
The scriptural way to begin the new month is by the conjunction of the moon, instead of visual observance of a crescent moon which came out of Babylon.
So the next question would be, when do we calculate the beginning of the new month, on the day of conjunction or wait until sunset of that day?
First of all let‘s define what a conjunction is.
According to the Encyclopedia Britannia in astronomy, a conjunction is an apparent meeting or passing of two or more celestial bodies at the same celestial longitude. The Moon is in conjunction with the Sun at the phase of New Moon, when it moves between the Earth and Sun and the side turned toward the Earth is dark.
There are several fallacies connected with the conjunction. One is that it happens at every place on earth, at the same time all over the earth. It is because of this false belief that some keep the new moon on the day of conjunction, starting the evening before, even though this may be up to 23 hours before the actual conjunction, and is still the last day of the old month.
Some of these same people will contest that we cannot start the year before the vernal equinox, because you would be starting a new year before the old year is over. Although we also believe that the year cannot start until the changing from winter to summer, this is a total contradiction to starting every new month before the actual conjunction really happens.
The problem is with some people‘s flawed definition of what a conjunction is.
Basically from the above definition we see that a conjunction is basically an eclipse of the moon, due to it lining up between the earth and sun, and causing one side to be basically dark. Because the rotation of the moon is elliptical and not circular, the moon is actually never 100% dark, but still cannot be seen with the naked eye. Logic will tell you that if an eclipse is happening at one place it cannot be happening of the other side of the globe in another place at the same time. So although the New Moon conjunction happens at only one moment in time roughly each 29 and ½ days, it does not occur at every place on earth. By the very definition of a conjunction the celestial bodies (in this case the moon, sun and earth) must be in the same longitude. When the moon is in conjunction with the earth at Rosh Codesh, the whole earth is not in the same longitude, only the area where the conjunction occurs.
So cunjunction DOES NOT happen in every place all over the earth, at the same time, although it does happen at only one moment of time roughly every 29 ½ days.
So the conjunction would happen at one spot on earth which would trigger the new moon or month in that area where sunset would just be occuring, then just like we do each week with the Sabbath we would wait, according to where we are on the earth for the earth to rotate on its axis, and the new month to come to us whenever it would be sunset in our given area. We do not start the Sabbath at 12:00 noon because it is suset in Jerusalem, so why would we start the new month in some cases 23 hours or more before the old month has ended because a sunset or conjunction has occurred across the world somewhere?
The next false assumption for some to start the month on the day of conjunction, instead of waiting for the next sunset, is that some have said that you celebrate your anniversary on the day of your anniversary, not the next day. On the surface this sounds logical, but if my anniversary were on Day X, I am not going to start to celebrate my anniversary on the Day before because it has already turned to Day X in Israel. By waiting till sunset in your given area after a conjunction has happened somewhere on earth, is not starting your month late. The month started whereever the conjunction occured on earth, and you are simply waiting for the earth to rotate and sunset and the new month to come to you, just as we do each and every Sabbath.