The reckoning of a symbolic day as a year in interpreting time periods in symbolic prophecy. The biblical texts generally cited for this are Num. 14:34 and Ezra 4:6 , both of which mention a “day for a year.” This principle, used from medieval times for some of the periods in the books of Daniel and Revelation, became a basic part of the standard Protestant school of interpretation, called the historical, or historicist, view of prophecy. Seventh-day Adventists, being historicists, have inherited this method of interpretation from the earlier commentators.
According to the year-day principle, a symbolic day in prophecy stands for a literal year, but a symbolic year stands for the same number of actual years as there are days in the symbolic year. The 1335 prophetic days ( Dan. 12:12 ) are thus interpreted as 1335 actual years; the three and a half prophetic years (as derived from the phrase “a time, and times, and half a time,” Rev. 12:14 ; cf. Dan. 7:25 ) are 31/2 x 360 = 1260 prophetic days, or 1260 actual years.
The 360-day year was formerly explained by some of the older commentaries as a “Jewish calendar year,” but there is no known straight 360-day calendar year; the Jewish year is lunar, with variable months of 29 and 30 days, and with 12 or 13 months (see SDADic : “Year” ). The later explanation of the 360-day prophetic year is based on the equivalence of several prophetic periods in Revelation: “A time, and times, and half a time” = 1260 days ( Rev. 12:6 , 14 ) = 42 months ( Rev. 11:2 , 3 ); and 42 months = 31/2 12-month years; therefore, these are theoretical months of 30 days each, and the symbolic year must be reckoned as 360 symbolic days.