A Lunar calendar is 354 days. 10 days less than a solar calendar of 364 days. This you can document and the book Enoch makes it very clear. 5 days less for the moon for a half year. (10 days for a year)

Enoch:
“4. Its period is less than that of the sun, according to the ordinance of the stars, by five days in one half year precisely.”

For the Islamic calendar the year begins in Muharram. This is the Angle of the sun in of Leo. And the moon at its first crescent in Leo.

But its the 10TH day of the moon after the first crescent that is celebrated. Called Ashura. It means 10TH.

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I will come back to that 10.

The significance of understanding that the first crescent is the REAL New Moon is huge.

The proof that the first crescent is the real NEW MOON is also stated in the Book of Enoch:

“And when it is wholly extinguished, its light is consumed in heaven; and on the first day it is called the new moon, for on that day light is received into it.”

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The first day after black moon is when the moon gets its first light, which is called New Moon.

So, Ashura is celebrated 10 days after first crescent or the real new moon and the beginning of the Lunar year. 10 days after the sun enters Leo.

The Book of Exodus also speaks of the beginning of the year. It starts the year in the Lamb/Male Lamb/Aries but also makes mention of the start being the 10th day in lamb/Ram/Aries:

“1 And the LORD spake unto Moses and Aaron in the land of Egypt, saying,

2 This month shall be unto you the beginning of months: it shall be the first month of the year to you.

3 Speak ye unto all the congregation of Israel, saying, In the tenth day of this month they shall take to them every man a lamb, according to the house of their fathers, a lamb for an house”

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The beginning is The Sun in Aries, first of the moon in Aries, and on the 10th day the Lamb/Aries moon is taken to LEO.

And the Islamic calendar beginning is, the sun in LEO.

1) Both are representing angles of the Sun and Moon on their ecliptic (vortex), which is tropical astrology.

2) Both are making it clear that the beginning is 10 days after the sun enters the angle and after the first crescent.