This is an important subject. The "Cosmic Week" theory makes Mrs. White's comment that "The Lord could have come err this" heresy. And the chapter of the SDABC the Role of Israel in Old Testament prophecy equally a lie.
God has given his people different times that could have finished the work and the end come, dating back to Biblical times. To study the text in their current framework of eschatology gives us information on how to apply the prophecies to our day. But the "Cosmic Week" destroys this way how God is trying to reach us. 1844 was the dawn of the age of exegesis that has opened the doors to where we can study this context.
Also, those who like the cosmic week heresy turn to the texts that says that a day to the Lord is like a thousand years and a thousand years as a day. The context is how timeless God is. In Leviticus 23 and 25 and here and there in Deuteronomy gives the Hebrew cycles. As Leviticus 23 points out the Hebrew week was 6 days and the Sabbath, 6 months and the Passover or Day of Atonement, 6 years and the Sabbatical year, and while not in Deuteronomy, 6 Sabbatical years and the Jubilee. Thus the Hebrew cycles are the day, the growing season (or half year) the full year, and in some cases the Sabbatical year. None of these passages speaking directly about the time cycle includes "Day = Thousand years" and the texts that say that a day to the Lord is like a thousand years and a thousand years like a day does not include the words "Oh, the Holy Spirit forgot to bring this up in the passages which discuss the Hebrew cycles. so please add these words to Leviticus and Deuteronomy". The cosmic week is taking a couple of texts out of context and ignoring the texts who's context is dealing with these cycles. Thus it is preparing hearts to how Satan will use the Bible when he comes claiming to be Jesus.