The Watchtower applies the "day for a year" principle when calculating the 7 times in Daniel 4: 23,25 for their 607BCE - 1914CE chronology (A time = 360 years based on Rev 11:3, 12:6 and 13:5. 7 times = 2520 years).
However, they do not use the "day for a year" principle for interpreting Daniel 12:11 (1290 days), Daniel 12:12 (1335 days) and Daniel 8:14 (2300 days). I believe that early on, C T Russell viewed the 1290, 1335 & 2300 days as years and made some predictions based on calculating these periods from starting dates related to the Catholic papacy. Interestingly, Sir Isaac Newton also adopted this interpretative methodology in his life-long studies on bible prophecy (Newton made various date predictions but as he got older he pushed the date further and further out until finally settling on 2060 AD for the earliest date by which Christ would return: this was calculated by simply counting 1260 years from 800 AD when the Holy Roman Empire began.)
However, the present Watchtower interpretation is that the 1290, 1335 and 2300 days are more or less literal days fulfilled by modern Watchtower organisation events, I think mostly declarations and pronouncements at 'landmark' conventions of the Bible Students in the 1920's (which is preposterous).
It seems to me that if the Watchtower is to treat the 1260 days in Revelation 11:3 and 12:6 as years (not days) when calculating their 1914 chronology, then they should also do the same for interpreting the 1290, 1335 and 2300 days in Daniel. Their inconsistency in treating these similar prophetic time periods is contradictory.
Yadda