This seven-year week may be further divided into two periods of 3.5 years each, from the two 3.5-year periods in Daniel's prophecy where the last seven years are divided into two 3.5-year periods, ( ) The time period for these beliefs is also based on other passages : in the book of Daniel, " time, times, and half a time ", interpreted as " a year, two years, and half a year, " and the Book of Revelation, " a thousand two hundred and threescore days " and " forty and two months " ( the prophetic month averaging 30 days, hence 1260 / 30 = 42 months or 3.5 years ).