The first month declared by Moses was Nissan/Abib.

 

Exodus 12:18 "In the first month, on the fourteenth day of the month at even, ye shall eat unleavened bread, until the one and twentieth day of the month at even."

 

Genesis 7:11 "In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened."

 

I believe this was Enoch's 2nd month and our 1st month later after the Exodus from Egypt.  Tishri was the 7th month and sometimes on the Hebrew calendar it was in October. 

 

Genesis 8:13-16 "And it came to pass in the six hundredth and first year, in the first month, the first day of the month, the waters were dried up from off the earth: and Noah removed the covering of the ark, and looked, and, behold, the face of the ground was dry. [14] And in the second month, on the seven and twentieth day of the month, was the earth dried.
    [15] And God spake unto Noah, saying, [16] Go forth of the ark, thou, and thy wife, and thy sons, and thy sons' wives with thee." 

 

The Book of Jubilees says that Noah came out on the new moon of the third month.  That means according to Enoch's calendar of 364 days Noah came out exactly 365 days later.  God had stretched out the heavens and added 1 full day of 24 hours: each month had 28 days and there were 13 months.  The new moon now came around every 29 days after that but they were not supposed to use the new moon; all they had to do was add 1 day to the second month [Nissan 29]. It's all right there in Scripture.    

 

Later, in the time of Hezekiah when he was sick unto death, God again stretched out the heavens and added a quarter of a day [6 hrs].  There afterwards 1 full day was added every fourth year as a leap year so Nissan then became 30 days long.  That 10 degrees backwards on the dial of Ahaz explains the  phenomena.  

 

My take upon the matter,  jfh