This information is given with the understanding that the reader is already somewhat familiar with most calendar terms and issues.
It all begins with Be'reshit (Genesis):
Gen 1:14 And Elohim said, "Let lights come to be in the expanse of the heavens to separate the day from the night, and let them be for signs and appointed times, and for days and years, Gen 1:15 and let them be for lights in the expanse of the heavens to give light on the earth." And it came to be so. Gen 1:16 And Elohim made two great lights: the greater light to rule the day, and the lesser light to rule the night, and the stars. Gen 1:17 And Elohim set them in the expanse of the heavens to give light on the earth, Gen 1:18 and to rule over the day and over the night, and to separate the light from the darkness. And Elohim saw that it was good. Gen 1:19 And there came to be evening and there came to be morning, the fourth day.
We see that the lights were given for:
Separating The Day From The Night Giving Light On the Earth Signs Appointed Times Days Years
When we observe the lights that YHWH says shows us His calendar, we see certain distinct events that only He has made: Equinox Conjunction Sunset
We use the Spring Equinox to determine the beginning of the Year because once the Spring Equinox occurs; it makes the next New Month significant.
Similarly, we use the Conjunction to determine the beginning of the Month, because once the Conjunction occurs, it makes the next Sunset significant.
So, in order to determine the First Day of the First Month of the New Year, we simply wait for the Spring Equinox, and then wait for the next Conjunction, then we wait for the next Sunset.
Everything in it’s order, using the given delineator events to establish the next new time period.
Spring Equinox --> Conjunction --> Sunset = 1st Day of the First Month of the New Year.
For those who are not familiar with the ease of using the distinct event called the Conjunction, it is a simple matter of noting the waning crescent disappearing in the morning sky. When the waning crescent is no longer seen in the morning immediately prior to sunrise, the coming Sunset starts the First Day of the New Month. Remember, a Month will only have 29 or 30 days, so there is NOTHING complicated about this, and it is not like it is a matter of having to wait out on your porch at sunrise for weeks on end. Something to consider is that YHWH starts the Day with the going down of the Sun, just like He starts the Month, with the going down of the Moon. Isa 60:20 "No longer does your sun go down, nor your moon withdraw itself, for YHWH shall be your everlasting light, and the days of your mourning shall be ended.
If we manipulate the calendar for our convenience instead of merely taking note of the events that YHWH has put in the sky (beyond our tampering), then we run the risk of missing His mark.
If we start an event before it happens, we are missing the mark.
Here is a link to a graphic that shows the difference: http://www.waytruthlife.com/images/Month_begins2.jpg [0] Something to consider - using this calendar: 1) The Spring Feasts will always be in the Spring (even Rishon Chodesh)
2) The Fall Feasts will always be in the Fall (even Yom Teruah)
3) The Full Moon will always be in the middle of the month (14th/15th)
4) We are using the signs in the sky that YHWH put there for that purpose.
5) In the rotation of things, nothing goes backwards. (except by YHWH's intervention) It is only man's ideas that will make a calendar event happen before it's time.