The Biblical calendar was set by the priests, according to the cycle of the Moon and the number of days lost.
Book of Jubilees, Chapter 6
1 And on the new moon of the third month he went forth from the ark, and built an altar on that mountain.
2 And he made atonement for the earth, and took a kid and made atonement by its blood for all the guilt of the earth; for everything that had been on it had been destroyed, sparing those that were in the ark with Noah.
3 And he placed the fat thereof on the altar, and he took an ox, and a goat, and a sheep and kids, and salt, and a turtle-dove, and the young of a dove, and placed a burnt sacrifice on the altar, and poured thereon an offering mingled with oil, and sprinkled wine and strewed frankincense over everything, and caused a goodly savour to arise, acceptable before the Lord.
4 And the Lord smelt the goodly savour, and He made a covenant with him that there should not be any more a flood to destroy the earth; that all the days of the earth seed-time and harvest should never cease; cold and heat, and summer and winter, and day and night should not change their order, nor cease forever.
5 And you, increase yourselves and multiply upon the earth, and become many upon it, and be a blessing upon it.
6 The fear of you and the dread of you I will inspire in everything that is on earth and in the sea. And behold I have given unto you all beasts, and all winged things, and everything that moves on the earth, and the fish in the waters, and all things for food; as the green herbs, I have given you all things to eat.
7 But flesh, with the life thereof, with the blood, ye shall not eat; for the life of all flesh is in the blood, lest your blood of your lives be required.
8 And at the hand of every man, and at the hand of every (beast) will I require the blood of man.
9 Who ever sheds man's blood by man shall his blood be shed, for in the image of God He made man.
10 And you, increase yourselves, and multiply on the earth.'
11 And Noah and his sons swore that they would not eat any blood that was in any flesh, and he made a covenant before the Lord God forever throughout all the generations of the earth in this month.
12 On this account He spoke to you, that you should make a covenant with the children of Israel in this month upon the mountain with an oath, and that you should sprinkle blood upon them because of all the words of the covenant, which the Lord made with them forever. And this testimony is written concerning you that you should observe it continually, so that you should not eat on any day any blood of beasts or birds or cattle during all the days of the earth, and the man who eats the blood of beast or of cattle or of birds during all the days of the earth, he and his seed shall be rooted out of the land.
13 And you are to command the children of Israel to eat no blood, so that their names and their seed may be before the Lord our God continually.
14 And for this law there is no limit of days, for it is forever. They shall observe it throughout their generations, so that they may continue supplicating on your behalf with blood before the altar; every day and at the time of morning and evening they shall seek forgiveness on your behalf perpetually before the Lord, that they may keep it and not be rooted out.
15 And He gave to Noah and his sons a sign that there should not again be a flood on the earth.
16 He set His bow in the clouds for a sign of the eternal covenant that there should not again be a flood on the earth to destroy it all the days of the earth.
17 For this reason it is ordained and written on the heavenly tablets, that they should celebrate the feast of weeks in this month once a year, to renew the covenant every year.
18 And this whole festival was celebrated in heaven from the day of creation till the days of Noah, twenty six Jubilees and five weeks of years, and Noah and his sons observed it for seven jubilees and one week of years, till the day of Noah's death, and from the day of Noah's death his sons did away with (it) until the days of Abraham, and they ate blood.
19 But Abraham observed it, and Isaac and Jacob and his children observed it up to your days, and in thy days the children of Israel forgot it until you celebrated it anew on this mountain.
20 And do you command the children of Israel to observe this festival in all their generations for a commandment unto them: one day in the year in this month they shall celebrate the festival.
21 For it is the feast of weeks and the feast of first fruits according to what is written and engraven concerning it, celebrate it.
22 For I have written in the book of the first law, in that which I have written for you, that you should celebrate it in its season, one day in the year, and I explained to you its sacrifices that the children of Israel should remember and should celebrate it throughout their generations in this month, one day in every year.
23 And on the new moon of the first month, and on the new moon of the fourth month, and on the new moon of the seventh month, and on the new moon of the tenth month are the days of remembrance, and the days of the seasons in the four divisions of the year. These are written and ordained as a testimony forever.
24 And Noah ordained them for himself as feasts for the generations forever, so that they have become thereby a memorial unto him.
25 And on the new moon of the first month he was bidden to make for himself an ark, and on that (day) the earth became dry and he opened (the ark) and saw the earth.
26 And on the new moon of the fourth month the mouths of the depths of the abyss beneath were closed.
27 And on the new moon of the seventh month all the mouths of the abysses of the earth were opened, and the waters began to descend into them.
28 And on the new moon of the tenth month the tops of the mountains were seen, and Noah was glad. And on this account he ordained them for himself as feasts for a memorial for ever, and thus are they ordained.
29 And they placed them on the heavenly tablets, each had thirteen weeks; from one to another (passed) their memorial, from the first to the second, and from the second to the third, and from the third to the fourth.
30 And all the days of the commandment will be fifty two weeks of days, and (these will make) the entire year complete. Thus it is engraven and ordained on the heavenly tablets.
31 And there is no neglecting (this commandment) for a single year or from year to year.
32 And you are to command the children of Israel that they observe the years according to this reckoning, three hundred and sixty four days, and (these) will constitute a complete year, and they will not disturb its time from its days and from its feasts; for everything will fall out in them according to their testimony, and they will not leave out any day nor disturb any feasts.
33 But if they do neglect and do not observe them according to His commandment, then they will disturb all their seasons and the years will be dislodged from this (order.) And they will disturb the seasons, and the years will be dislodged, and they will neglect their ordinances.
34 And all the children of Israel will forget and will not find the path of the years, and will forget the new moons, and seasons, and Sabbaths and they will go wrong as to all the order of the years.
35 For I know and from henceforth will I declare it unto thee, and it is not of my own devising; for the book (sets) written before me, and on the heavenly tablets the division of days is ordained, lest they forget the feasts of the covenant and walk according to the feasts of the Gentiles after their error and after their ignorance.
36 For there will be those who will assuredly make observations of the moon, how (it) disturbs the seasons and comes in from year to year ten days too soon.
37 For this reason the years will come upon them when they will disturb (the order), and make an abomination the day of testimony, and an unclean day a feast day, and they will confound all the days, the holy with the unclean, and the unclean day with the holy; for they will go wrong as to the months and Sabbaths and feasts and Jubilees.
38 For this reason I command and testify to you that you must testify to them; for after your death your children will disturb (them), so that they will not make the year three hundred and sixty four days only, and for this reason they will go wrong as to the new moons and seasons and Sabbaths and festivals, and they will eat all kinds of blood with all kinds of flesh.
The Holy Hebrew Solar Calendar was replaced by the Hellenist in 167 BC with the Lunar Calendar. The Hellenist took over the temple from the priesthood in charge at that time. The Hellenist were a secret society that consisted of mainly the wealthy. This event is what lead to the Civil Hebrew Calendar.