The book of Jubilees, sometimes called Lesser Genesis, was discovered in the caves of Qumran along side the oldest copies of Genesis in existence. These manuscripts date back to 200 BC, and predate the Masoretic text. Jubilees gives a clue as to which months, sabbaths and festivals Yahweh was not pleased with. These are the same days Paul refers to when talking to the Galatians.
Jubilees Chapter 1: 1 And it came to pass in the first year of the exodus of the children of Yisrael out of Egypt, in the third month, on the sixteenth day of the month, [2450 Anno Mundi] that YAHWEH spoke to Mosheh, saying: ‘Come up to Me on the Mount, and I will give you two tables of stone of the Torah and of the commandment, which I have written, that you may teach them.’
2 And Mosheh went up into the mount of YAHWEH, and the splendor of YAHWEH abode on Mount Sinai, and a cloud overshadowed it six days.
3 And He called to Mosheh on the seventh day out of the midst of the cloud, and the appearance of the splendor of YAHWEH was like a flaming fire on the top of the mount.
4 And Mosheh was on the Mount forty days and forty nights, and YAHWEH taught him the earlier and the later history of the division of all the days of the Torah and of the testimony.
5 And He said: ‘Incline your heart to every word which I shall speak to you on this mount, and write them in a book in order that their generations may see how I have not forsaken them for all the evil which they have wrought in transgressing the covenant which I establish between Me and you for their generations this day on Mount Sinai.
6 And thus it will come to pass when all these things come upon them, that they will recognise that I am more righteous than they in all their judgments and in all their actions, and they will recognise that I have been truly with them.
7 And do you write for yourself all these words which I declare unto, you this day, for I know their rebellion and their stiff neck, before I bring them into the land of which I swore to their fathers, to Abraham and to Yitschaq and to Yacob, saying: ‘ Unto your seed will I give a land flowing with milk and honey.
8 And they will eat and be satisfied, and they will turn to strange gods, to (gods) which cannot deliver them from aught of their tribulation: and this witness shall be heard for a witness against them. For they will forget all My commandments, (even) all that I command them, and they will walk after the Gentiles, and after their uncleanness, and after their shame, and will serve their gods, and these will prove unto them an offence and a tribulation and an affliction and a snare.
10 And many will perish and they will be taken captive, and will fall into the hands of the enemy, because they have forsaken My ordinances and My commandments, and the festivals of My covenant, and My Shabbats, and My kodesh place which I have hallowed for Myself in their midst, and My tabernacle, and My sanctuary, which I have hallowed for Myself in the midst of the land, that I should set MY NAME upon it, and that it should dwell (there).
11 And they will make to themselves high places and groves and graven images, and they will worship, each his own (graven image), so as to go astray, and they will sacrifice their children to demons, and to all the works of the error of their hearts.
12 And I will send witnesses unto them, that I may witness against them, but they will not hear, and will slay the witnesses also, and they will persecute those who seek the torah, and they will abrogate and change everything so as to work evil before My eyes.
13 And I will hide My face from them, and I will deliver them into the hand of the Gentiles for captivity, and for a prey, and for devouring, and I will remove them from the midst of the land, and I will scatter them amongst the Gentiles.
14 And they will forget all My Torah and all My commandments and all My judgments, and will go astray as to new months, and Shabbats, and festivals, and jubilees, and ordinances.
15 And after this they will turn to Me from amongst the Gentiles with all their heart and with all their soul and with all their strength, and I will gather them from amongst all the Gentiles, and they will seek me, so that I shall be found of them, when they seek me with all their heart and with all their soul.
16 And I will disclose to them abounding shalom with righteousness, and I will remove them the plant of uprightness, with all My heart and with all My soul, and they shall be for a blessing and not for a curse, and they shall be the head and not the tail.
17 And I will build My sanctuary in their midst, and I will dwell with them, and I will be YAHWEH their Sovereign Ruler and they shall be My people in truth and righteousness.
18 And I will not forsake them nor fail them; for I am YAHWEH their Sovereign Ruler.’
19 And Mosheh fell on his face and prayed and said, ‘O YAHWEH my Sovereign Ruler, do not forsake Your people and Your inheritance, so that they should wander in the error of their hearts, and do not deliver them into the hands of their enemies, the Gentiles, lest they should rule over them and cause them to sin against You.
20 Let your mercy, O YAHWEH, be lifted up upon Your people, and create in them an upright spirit, and let not the spirit of Belial rule over them to accuse them before You, and to ensnare them from all the paths of righteousness, so that they may perish from before Your face.
Compare to Paul’s letter to the Galatians:
Gal 4:8 Howbeit then, when ye knew not God, ye did service unto them which by nature are no gods.
Gal 4:9 But now, after that ye have known God, or rather are known of God, how turn ye again to the weak and beggarly elements, whereunto ye desire again to be in bondage?
Gal 4:10 Ye observe days, and months, and times, and years.
Gal 4:11 I am afraid of you, lest I have bestowed upon you labour in vain.
Does anyone seriously think Paul is calling Yahweh’s appointed times, sabbaths and feast days weak and beggerly? Paul was recorded as still keeping the feasts in the book of Acts. Also his manner was to keep the sabbath.
Act 18:21 But bade them farewell, saying, I must by all means keep this feast that cometh in Jerusalem: but I will return again unto you, if God will. And he sailed from Ephesus. KJV
Act 17:2 And Paul, as his manner was, went in unto them, and three sabbath days reasoned with them out of the scriptures,
Act 17:3 Opening and alleging, that Christ must needs have suffered, and risen again from the dead; and that this Jesus, whom I preach unto you, is Christ. KJV