It is not surprising that Jesus endorsed this principle. After all he gave the prophecies to both Daniel and John the Revelator.
Here is a time prophecy in Daniel chapter 9:24-27
Seventy weeks are determined upon thy people and upon thy holy city, to finish the transgression, and to make an end of sins, and to make reconciliation for iniquity, and to bring in everlasting righteousness, and to seal up the vision and prophecy, and to anoint the most Holy. Know therefore and understand, [that] from the going forth of the commandment to restore and to build Jerusalem unto the Messiah the Prince [shall be] seven weeks, and threescore and two weeks: the street shall be built again, and the wall, even in troublous times. And after threescore and two weeks shall Messiah be cut off, but not for himself: and the people of the prince that shall come shall destroy the city and the sanctuary; and the end thereof [shall be] with a flood, and unto the end of the war desolations are determined. And he shall confirm the covenant with many for one week: and in the midst of the week he shall cause the sacrifice and the oblation to cease, and for the overspreading of abominations he shall make [it] desolate, even until the consummation, and that determined shall be poured upon the desolate.
Seventy weeks in the Day = Year Bible time prophecy would be:
70 weeks with 7 days in a week => 70x7=490 days, therefore, 490 years.
Note what might appear to be a strange answer Jesus gives Peter in the following passage in Matthew 18:21,22
"Then came Peter to him, and said, Lord, how oft shall my brother sin against me, and I forgive him? till seven times? Jesus saith unto him, I say not unto thee, Until seven times: but, Until seventy times seven."
What Jesus is trying to awaken Peter to is the 70 weeks prophecy of Daniel 9. He is telling Peter to consider how long God has put up with the nation's transgression, sin and iniquity. He is reminding Peter that the 70 weeks prophecy of Daniel 9 was about to come to a close. God (for)gave the nation of Israel 490 years, to make an end of sin, transgression and iniquity and you, Peter, are asking me to forgive a brother only seven times? No, you ought to forgive him 70x7= 490 times, like I have done with Israel. Jesus was indirectly endorsing the Day=Year principle for the time prophecies.
MAJOR TIME PROPHECIES IN DANIEL & REVELATION:
Daniel 7:25 - time, times and half a time (1260 days cf Rev 12:6,14))
Daniel 8:14 - 2300 days
Daniel 12:7 - time, times and a half (1260 days cf Rev 12:6,14))
Daniel 12:11 - 1290 days
Daniel 12:12 - 1335 days
Revelation 11:3 - 1260 days
Revelation 12:6 - 1260 days
Revelation 12:14 - time, and times and half a time (1260 days cf Rev 12:6,14))
Revelation 13: 5 - 42 months = 1260 days (30 days in a Biblical month)
TIME PERIODS IN THE PROPHECIES OF DANIEL AND THE REVELATION Many modern teachers unknowingly or knowingly follow the Roman Catholic Jesuits, Ribera and Bellarmine in claiming that the time periods in Daniel and Revelation are to be taken literally and apply to the future. However many scholars, Jewish and Christian, from before Christ to the modern day, have understood the time periods to be symbolic of longer periods of time, most of which have been fulfilled in the past.
Several clues show which prophetic periods are symbolic of longer periods of literal time:
(1) Symbolic CONTEXT Most time prophecies in Daniel and the Revelation are given in symbolic contexts. This suggests that the associated time periods are also symbolic.
(2) Symbolic time UNITS “EVENING MORNINGS” [Hebrew ereb bo- qer] of Dan 8:14 (margin) and 8:26 are an unusual way of expressing days. The usual Hebrew word for “days” is yowm. 3 1/2 “TIMES” (Dan 7) are an unusual way of expressing years. The “WEEKS” in the 70 weeks are an unusual unit to use in expressing a period of this length. The use of such unusual time units is intended to indicate that these periods are not literal time but symbolic time.
(3) Symbolic time PERIODS 70 weeks, 1260 days, 1290 days, 1335 days, 2300 days are unusual ways of expressing periods of this length. A Hebrew would normally say 6 years and four months, not 2300 days. Literal time is expressed as a number of years, months and days. e.g. in Elijahʼs day, “heaven was shut up three years and six months.” (Luke 4:25). “...it rained not on the earth by the space of three years and six months.” (James 5:17). “David was king in Hebron over the house of Judah was seven years and six months..” (2Sam 2:11).
Jehoachin “...reigned three months and ten days.“(2Chron 36:9). The use of unusual time quantities (70 weeks, 1260 days, 3 1/2 “times”, 1290 days, 1335 days, 2300 days) in prophecy indicates that these periods are not usual literal time periods but symbolic time periods.
(4) Small periods in big contexts Daniel & Revelation concern BIG subjects, such as the rise, reign and fall of historyʼs great kingdoms, and yet relatively SMALL periods (3 1/2 days, 1260 days, 1290 days, 1335 days, 2300 days). Other prophecies, such as Israelʼs captivities in Egypt & Babylon, concern SMALLER subjects (the experiences of Israel) but appear to have BIGGER periods (400 years, 70 years). The solution to this paradox is that the small periods of Daniel & Revelation are actually symbolic of much larger periods of time.
(5) The appropriateness of scale Only if taken symbolically can the prophetic periods accommodate the subjects under discussion. e.g. the 2300 days of Daniel 8 span Medo-Persia, Greece and Rome and reach to the “time of the end” (v 17). Only if taken symbolically can 2300 “days” accommodate the period of these kingdoms. The “one day” in Rev 18:8 in which a “famine” will occur is evidently symbolic of a period long enough to have a famine.
(6) The 70 weeks The first 69 of the 70 “weeks” of Dan 9:25 reached from the commandment to restore Jerusalem, which went forth over 450 years before Christ, to Christ. The 69 “weeks” or 483 days, therefore symbolize a period of over 483 years. Note: The period was “70 shabua (“weeks)” not “sevens” or “sevens of years,” as found in some translations. Shabua always means a period of seven days - a week. Christ declared, “The time is fulfilled,” doubtless referring to the 69 weeks which were to reach to the appearing of the Mes- siah. Thus Christ Himself verified that the days of the 69 “weeks” symbolized years. Preterists and Futurists are both compelled to acknowledge the day-for-a-year rule in the 70 week prophecy.
Having discovered the clues which show which periods are symbolic, what are they symbolic of?
Hebrew poetry parallels days with years “[Are] thy days as the days of man? [are] thy years as manʼs days.” Job 10:5 “I said, Days should speak, and multitude of years should teach wisdom.” Job 32:7 “I have considered the days of old, the years of ancient times.” Psalms 77:5.
The Sabbatical year (Exo 23:10-11) The week of 7 days provided the pattern for the ʻweekʼ of 7 years in which the land rested, uncultivated, every 7th year.
The Day = Year Principle Num 14:34 “ ...each day for a year...” Eze 4:6 “I have appointed thee each day for a year.”
CONCLUSION Symbolic days represent literal years.
APPLICATION One must first determine if a period is literal or symbolic. Those that are symbolic can be identified as such by the principles previously outlined. Each symbolic period must then be converted to symbolic days, and each symbolic day represents a literal year. e.g. 70 weeks = 490 days = 490 years. e.g. 3 1/2 times = 1260 days = 1260 years. e.g. 2300 days = 2300 days = 2300 years. When understood this way the prophetic periods perfectly fit historical events.
Pragmatic test When days are taken as symbols for years in symbolic periods these periods meet accurate fulfillments. e.g. 69 ʻweeksʼ were to reach from the commandment to restore and build Jerusalem to the Messiah. When the first 69 ʻweeksʼ (483 days) are taken to symbolize 483 years, they reach from the commandment to the appearance of Messiah. This pragmatic test confirms the day = year principle. Could the prophetic periods have another application as literal days? To reapply the symbolic periods in the future as literal days would require one to deny all the evidences which shows that the periods are symbolic, not literal.
Historic use of the year-day principle In the third century B.C. the translators of the Septuagint, the Greek Bible, inserted the phrase “weeks of years” in the 70 week prophecy of Daniel 9. “Nahawendi, in the early ninth century, was evidently the first to interpret the 1290 and 2300 days as years. Then Saadia, Jeroham, Hakohen, Jepphet idn Ali, and Rashi of the tenth century applied it not only to the 70 weeks but also to one or more of the 1290, 1335, and 2300 day periods. And Hanasi and Eliezer, in the eleventh and twelfth centuries, and Nahmanides in the thirteenth, similary extended it to the longer time periods of Daniel.” L.E. Froom, The Prophetic Faith of our Fathers, R&H 1950, Vol. I, p713.
In the centuries following, the day-year principle came to be widely accepted and was the method accepted by most of the Protestant Reformers.