Badboy,
I think you understate the problem with this aspect of the Watchtower's 1914 interpretation. There are several calendar related problems with this interpretation.
First, JWs tell us that the "times" of Daniel 4 referred to "prophetic years" of 360 days each. Their belief is based on the idea that the "1260 days" spoken of in Revelation 12 are there equated with the "3 and 1/2 times" also there spoken of. But this is not necessarily so. (For instance, the 1260 days in Rev. 12:6 may possibly refer to the time when Christianity was protected between the time of Christ's ascension and the time the Spirit was poured out on the Gentiles in 36 AD. Then, when the good news began to be preached to all national groups Christianity took off, as though it had wings of eagles, and was thereafter protected for a second longer period of time. This second period of protection was the "3 and 1/2 times" spoken of in Rev. 12:14. This "3 and 1/2 times" would then be understood to be the period of time from 36 AD until the time of Christ's return.) Since some interpretations of Revelation 12, such as this one, say that the "1260 days" and the "3 and 1/2 times" do not refer to the same period of time, it is quite possible that the concept of a 360 day "prophetic year" does not even exist in the Bible.
Second, as you have pointed out, it seems contradictory that each of the 360 days in each of these 7 supposed "prophetic years" was meant to picture a solar year containing 365.24 days. For if days were meant to be understood as years, then it would follow that days in prophetic years ought to be understood as an equal number of 360 day "prophetic years," not an equal number of 365.24 day solar years.
Third, this interpretation of Daniel 4 is internally inconsistent with both Daniel and Revelation. The Watchtower's interpretation of Daniel 4 tells us that its "seven times" = 2,520 years. We are told that the cryptic word "times" clearly indicates a greater meaning than just "seven years." But when the term "3 and 1/2 times" (half of seven times) is used in both Daniel and Revelation (Dan. 8:25; Rev.12:14) the Watchtower does not say those "3 and 1/2 times" equal 1,260 years, half of 2,520 years. To do so would certainly be consistent with their Daniel 4 interpretation. But the Watchtower Society tells us that when the term "3 and 1/2 times" appears in the Bible it simply means 3 and 1/2 years and nothing more.
Finally, we should remember that the Jews used a lunar calendar which contained six months of 30 days and six months of 29 days, totaling 354 days. The Jews adjusted their lunar calendars by adding a thirteenth month to them every few years to prevent them from falling too far out of sync with the solar year. But the fact remains that a "year" to the Jews meant a 354 day lunar year, not a 365 day solar year, and definitely not a 360 day "prophetic" year. So, if the word "times" in Daniel 4 was meant to be understood as "years," Daniel almost certainly would have understood them as 354 day lunar years.
These are only the calendar related problems with the Watchtower's "1914" interpretation of Daniel 4. There are, of course, many more problems with it.