7 times = 2,520 days based on Revelation 12:6 and Revelation 12:14
2,520 ÷ 7 = 360 and 1,260 ÷ 3 1/2 times = 360
Therefore a year = 360 days which is confirmed in the Insight book (see Year - In Prophecy)
Numbers 14:34 and Ezekiel 4:6 are used to support "a day for a year."
The year 607 BC had 360.0 days according to the Israelite calendar and the Babylonish calendar, which was scripturally abandoned in 70 AD with the destruction of Jerusalem, some 678 years (of 360.0 days each) after the prophecy of Daniel regarding the "seven times."
Then suddenly we arrive at 1914 which has 365.25 days according to the Gregorian calendar (365.2425 days) which replaced the Julian calendar (365.25 days) introduced in 45 AD.
Daniel's prophecy was written under an Israelite 360.0 day / year calendar which in the 6th century BC had adopted Babylonish names from Babylon's lunation month of 29 or 30 days (360.0 day year), whereas the revelation of John was written under a Roman Julian calendar of 365.25 day / year while John was in a Roman prison. Watchtower's interpretation of the bible books of Daniel and Revelation was made under a Gregorian calendar introduced by Catholic Pope Gregory XIII in October 1582 AD.
You cannot cherry pick calendars and years when the bible is explicit on days and years with each year having either 360 days or 365.25 days.