From: http://www.beholdthebeast.com/mathematical_precision_of_prophecy.htm#the_multipliers
The use of prophetic day=year language is certainly nothing new. Indeed the interpretations in the church today are what are new, especially those from within the last hundred to few hundred years or so (futurism/preterism). As mentioned earlier, Scripture instructs us: Job 8:8 For enquire, I pray thee, of the former age, and prepare thyself to the search of their fathers: 9 (For we [are but of] yesterday, and know nothing, because our days upon earth [are] a shadow:)
Quoting from “The False Prophet”: “In 1569, the great Anabaptist theologian, Thieleman van Braght, wrote the following in Martyrs Mirror, pages 21-24: ‘a thousand two hundred and threescore days, which reckoned according to prophetic language means as many years… let it be reckoned as it may, say we, as a very long period of time.‘
Two hundred years later, Matthew Henry, in his ‘Commentary of the Whole Bible’, came to the same conclusion (Vol VI, page 1157 column 1, para. 2): “….if the beginning of that interval could be ascertained, this number of prophetic days, taking a day for a year, would give us a prospect of when the end might be.“
Isaac Newton – “She is nourished by the merchants of the earth, three times or years and an half, or 42 months, or 1260 days: and in these Prophecies days are put for years.” -Observations Upon the Prophecies of Daniel, and the Apocalypse of St.a John – Chapter 3
Even 19th century Jamison, Faucett & Brown commentary – “….. in the wilderness ‘a thousand two hundred and threescore days.’ In the wider sense, we may either adopt the year-day theory of 1260 years…“
“Whether we begin to reckon these years from the death of the apostles; or with the year 300, when the so-called patriarchs had their origin; or with the year 600; or a little later, when Mohammed rose in the east among the Greeks, and the pope in the west among the Latins, and raised no small persecution against the defenseless and innocent little flock of the church of Christ, so that all who did not wish to be devoured, either in soul or in body, had to hide themselves in deserts and wildernesses; let it be reckoned as it may, say we, a very long period is to be understood by it, which has extended to this, or about this time . . .” Thieleman J. van Braght – July 31, 1659AD, from pp21, 25, and 40 of Martyrs Mirror.
Ezekiel 4:5 For I have laid upon thee the years of their iniquity, according to the number of the days, three hundred and ninety days: so shalt thou bear the iniquity of the house of Israel.
Ezekiel 4:6 And when thou hast accomplished them, lie again on thy right side, and thou shalt bear the iniquity of the house of Judah forty days: I have appointed thee each day for a year.
Numbers 14:34 After the number of the days in which ye searched the land, [even] forty days, each day for a year, shall ye bear your iniquities, [even] forty years, and ye shall know my breach of promise.
Genesis 29:27 Fulfil her week, and we will give thee this also for the service which thou shalt serve with me yet seven other years.
Additionally Exodus alludes to a week of days as years:
Exodus 23:10 And six years thou shalt sow thy land, and shalt gather in the fruits thereof: 11 But the seventh [year] thou shalt let it rest and lie still; that the poor of thy people may eat: and what they leave the beasts of the field shall eat. In like manner thou shalt deal with thy vineyard, [and] with thy oliveyard.
Others who understood this language include:
Augustine (AD 430)
Nahawendi (Jewish) (AD 8-9th century)
Jehoram (AD 10th century)
Abraham bar Hiyya (Jewish) (AD 1136)
Arnold of Villanova AD (1292)
Tichonius (AD 380)
Joachim of Floris (AD 1202)
John Wycliffe (AD c.1379)
Nicholas of Cusa (AD c.1452)
Martin Luther (AD 1522)
Phillip Melanchthon (AD 1543)
Johan Funck (AD 1558)
James I of England (AD 1600)
Sir Isaac Newton (AD 1727)