The "days and months and seasons and years" of verse 10 do not refer to God's holy days, but rather to pagan, Gentile holidays that the Galatians observed before conversion in service to "those which by nature are not gods," as verse 8 says.
This, in turn, reinforces our understanding of "the elements of the world" in verse 3. It clearly does not say "the elements of God." Just like in Colossians 2, the "elements of the world" are clearly identified as being demons—personal powers that are capable of being worshipped. We are not dealing with something from God. However, they are elements, foundations, of the world.
A second important facet is that verse 3 mentions being "in bondage," that is, we were enslaved to the elements of the world. Bondage suggests something difficult to be borne, of oppression, of captivity, of withholding liberty. Notice James 2:11-12:
For He [God] who said, "Do not commit adultery," also said, "Do not murder." Now if you do not commit adultery, but you do murder, you have become a transgressor of the law. So speak and so do as those who will be judged by the law of liberty.
Consider this in relation to the bondage of Galatians 4:3. It puts these two concepts into direct opposition. There is a great difference between bondage and liberty; they are, in this sense, mutually exclusive. Galatians 4 is not talking about the law of God being a means of bondage.
Similarly, I John 5:3 says, "For this is the love of God, that we keep His commandments. And His commandments are not burdensome." Bondage is grievous, but keeping of God's law is not. Bondage gives a person difficulty, but keeping the commandments do not, for they are a law of liberty. Keeping God's commandments is freeing, liberating. It is not a burden. Love is never a burden but always supports, frees, and liberates.
It becomes very clear that the "elements of the world" and "bondage" of Galatians 4:3 do not refer to the law of God, nor does verse 10.
Judaism, though it was a very poor interpretation of God's Word, did at least have some basis in the Old Testament. When people read the book of Galatians and see all these references to "law" and "bondage," they immediately assume that Paul is speaking about Judaism. Indeed, Judaism is part of the picture, but not all of it. We can prove this from verse 9: "How is it that you turn again to the weak and beggarly elements. . . ?" It would be about as close to blasphemy as one could get if a person—in this case, God's apostle—were to call something that God gave, intended to be good and liberating, "weak and beggarly" and tending to "bondage"!
Thus, the "days and months and seasons and years" is not something Paul wrote in reference to the law of God or even to Judaism. Instead, they are something apart from both of them.
Though Judaism is clearly within the context of Galatians, so also is pagan Gnosticism—which wormed its way into the church primarily through people in the area becoming members of the church, and through church members' contacts with friends outside of the church. We can tell from books like I, II, and III John that Gnosticism eventually grew to dominate the church of God in Asia Minor.