When this passage is compared with Galatians 4:9 we can see that a connection in Paul's teaching is revealed: "But now that you have come to know God, or rather to be known by God, how is it that you turn back again to the weak and worthless elemental things, to which you desire to be enslaved all over again? You observe days and months and seasons and years." In verse 10, we read - "you observe..,"
days (weekly Sabbaths, corresponding to "Sabbath days in Colossians 2)
months (new moons, corresponding to "a new moon" in Colossians 2)
seasons (the 7 feasts, corresponding to "festivals" in Colossians 2)
and years (the sabbatical year and the 50th year of Jubilee)
Paul is clearing speaking about the observances of all Jewish holy days, including the weekly Sabbath. When God refers to the whole system of Jewish holy days, rather than naming them all, He would refer to the yearly, monthly and weekly as representing the whole system and yearly Sabbaths were already referred to in Colossians 2:16 as "festivals". The "Year, Month, Week" pattern is well established in the Old Testament and Colossians 2:16 does not exclude the weekly Sabbath.
Yearly, monthly, weekly pattern proves it is the weekly Sabbath
1 Chronicles 23:31 - Yearly (fixed festivals), monthly (new moons), weekly (Sabbaths)
2 Chronicles 2:4 - Yearly (appointed feasts), monthly (new moons), weekly (Sabbaths)
2 Chronicles 8:13 - Yearly (annual feasts), monthly (new moons), weekly (Sabbaths)
2 Chronicles 31:3 - Yearly (fixed festivals), monthly (new moons), weekly (Sabbaths)
Nehemiah 10:33 - Yearly (appointed times), monthly (new moon), weekly (Sabbaths)
Isaiah 1:13-14 - Yearly (appointed feasts), monthly (new moon), weekly (Sabbath)
Ezekiel 45:17 - Yearly (appointed feasts), monthly (new moons), weekly (Sabbaths)
Ezek 46:1-11 - Yearly (appointed feasts), monthly (new moons), weekly (Sabbath)
Hosea 2:11 - Yearly (festal assemblies), monthly (new moons), weekly (Sabbaths)
Galatians 4:10 - years, months, days
Colossians 2:16 - festival, new moon, Sabbath day
Amen! Galatians 3:10 - For as many as are of the works of the law are under the curse; for it is written, “Cursed is everyone who does not continue in all things which are written in the book of the law, to do them.” The SDA gospel culminates in salvation by "grace plus law, faith plus works." More than a subtle mixture of law and grace that is a perversion of the gospel. (Galatians 1:6-9)