Appendix A
The Prophetic Calendar
How Long is a Year?

There have been numerous calendars throughout history. A solar year is 365¼ days long. It’s clear from the texts in the table that the 3½ year period equals 42 months or 1,260 days. Simple arithmetic gives a 360 day year. In other words, for purposes of this prophecy, a "year" is supposedly 360 calendar years long.

The foundation of this idea is the 30 day Jewish month. But while the Jewish month is a nominal 30 days long, it’s not exactly 30 days long. The Jewish month is actually a lunar month. It begins the first day that the new moon is seen.

When the new moon was observed, the Sanhedrin was notified. When the committee (three members, including the High Priest) heard testimony from two independent, reliable eyewitnesses that the new moon occurred at a certain time, they would declare the rosh chodesh (first of the month) and send out messengers to tell people when the month began. This method of determining the rosh chodesh means that it’s entirely possible for a month to begin a day or two late if the weather prevents a good view of the sky. The Jews understood this, and allowed a month to go up to two extra days before they forced the new month to start.

Immediately we can see that Jewish months are variable in length. However, celestial events are not variable in their timing. The fundamental clock of the Jewish month, the moon, operates on a 29½ day cycle.(1) Note that this rounds off to 30 days. This gives the 30-day months in the prophecy above. But, since the cycle is not 30 days, it starts a day early every other month.

A twelve lunar month year will be 354 days long.(2) This is about 11 days less than the solar year that governs the seasons. A thirteen-month year would be about 19 days too long. Since the Bible requires certain feasts to be held during specific seasons, it’s necessary to have an adjustment to match the solar year. Also, since certain feasts weren’t allowed to be on particular days of the week, the lengths of some months are adjusted upward or downward by a day.(3)

In an ordinary year, there would be twelve months totaling 353, 354, or 355 days. In order to keep the festivals in harmony with the seasons, the Jews used intercalated months (an extra, 13th month). This leap year occurred seven out of nineteen years. This shifted the new year back 29 or 30 days, yielding a year from 382 to 385 days long. A year was never 360 days long.

Because of the immense importance of the proper timing of the holy festivals, the calendar was kept very carefully. The Old Testament shows this happened even during the Babylonian exile. These detailed records let us determine with great accuracy how the Jewish calendar corresponds with their neighbors’ calendars. We can also project our modern calendar backward into ancient times, and we can match it with all major ancient calendars.

Astronomy/astrology was an important part of all ancient cultures. Very detailed calendar records exist from all relevant cultures. We can confidently say that the Jews, Greeks, Persians, Egyptians, Romans, Babylonians, and others were well aware of the 365 ¼ day solar year. They started their years at different seasons and used different lengths and numbers of months. Their methods of adjustment to the solar year varied, but the results were the same, except for the Egyptians. They used a 360-day year in spite of the solar year, since they saw no problem from the months sliding with respect to the seasons.

But how long is the prophetic year? Or, in other words, how many "days/years" does it represent? The Jewish year is no help, since it was variable length. We know, as we have already noted, that the Jews kept their calendar records very carefully because the calendar had theological importance. Is it possible that God intended that the Jews should be so careful to keep his standard calendar, yet impose a different one when prophecy was to be considered?

The first and foremost consideration is that prophecy is understandable (2 Tim 3:15–16). It’s true that Daniel was told to "conceal these words and seal up the book" (Dan 12:4). But the book of Revelation clarifies the 1,260 day prophecy. That means Daniel wasn’t sealed any more. Therefore, the context of the prophecy is the calendar of the first century. Since the Jewish calendar hadn’t changed, it has to be the calendar we use to understand prophecy.

Next, we have to look at other prophecies.

For thus says the Lord, “When seventy years have been completed for Babylon, I will visit you and fulfill My good word to you, to bring you back to this place.” (Jer 29:10)

The historical and scriptural record for this prophecy is clear. When seventy standard solar years (by anyone’s calculations) were completed, Cyrus freed the Jews. If a 360-day prophetic year had been the standard, God was about a year late, since seventy of those "years" would be about 69 standard years.

Next we need to look at record-keeping. If prophetic years are 360 days long, it would be absolutely necessary to have a second set of records to establish when a prophecy was fulfilled. There is absolutely no evidence that the Jews ever kept a "prophetic 360-day year" calendar. But they were compulsive about keeping the standard calendar. Without this second calendar, there would be no chance that they would understand when any prophecy would be completed. As our study of Daniel 9 shows, the Jews (and even the Samaritans and the Magi) did understand the proper length of the seventy weeks, and they understood it to be 490 standard solar years.

Does it make any sense for God to give prophetic guidance that can’t be understood? Of course not! When God gave Daniel the prophecies of end times, God knew that the Jews kept a calendar synchronized with the solar year. When the prophecies were repeated to John, this situation hadn’t changed. If the 30-day month were the rule in prophecy, then there would be evidence that either the Jews knew it or that God had given instruction regarding it. Since we don’t have either, we must conclude that God had no intention of fitting prophecy into 360-day years.

We must ask why we need to even consider a 360-day year. After all, if the Jews didn’t have such a year, why would it even appear in prophecy? The simplest answer comes from the nature of apocalyptic prophecy. In it, long spans of time are represented in symbolic terms. Since these terms are figurative, they don’t fit well with the technical precision required to describe the Jewish year. It’s far more appropriate to say "forty-two months" (Rev 11:2) than to include a dissertation on the fine details of which months in which years should be counted. Such an aside would detract from the message the prophecy was intended to convey. It also allowed God to tell how many years were in the prophecy (on the "year for a day" principle) without dealing with the complexities of the nineteen year Metonic cycle.

The Jews knew that a month was (about) 30 days long. 42 months, or 1,260 days, would have seemed natural to them as a way of describing the time. At the same time, they would automatically know that it wasn’t an exact way of describing specific years, since the calendar didn’t have twelve 30-day months. This isn’t any different than our modern thinking, where "a month is 30 days", even though months may actually have 28, 29, 30, or 31 days.

Prophecies in symbolic language allow us to understand how many years they represent. They don’t say anything directly about how long those years are. That has to be determined by the culture of the writer. Jewish years are solar years of 365¼ days.