Biblical Years

What is a Year?

In the Bible, the word “year” can mean different things, but it never refers the Gregorian solar year on which our modern calendars are based. Most of the time, it refers to the Jewish calendar year, which was based on lunar cycles and the occasional inclusion of leap months.

However, there is another simpler type of “year” that was defined long before Israel or their Jewish calendar, and we see it used at various places in scripture, from Genesis to Revelation. This other type of year is often called a Biblical year (or sometimes a prophetic year). This type of year is exactly 360 days, consisting of twelve 30-day months.

Biblical Years in Scripture

We first see a glimpse of this simple 360-day year in the account of the flood of Noah, way back in Genesis. The relevant verses come from chapters 7 and 8:

  • Gen 7:11, In the six hundredth year of Noah’s life, in the second month, on the seventeenth day of the month, on the same day all the fountains of the great deep burst open, and the floodgates of the sky were opened.
  • Gen 7:24, The water prevailed upon the earth one hundred and fifty days.
  • Gen 8:3, and the water receded steadily from the earth, and at the end of one hundred and fifty days the water decreased.
  • Gen 8:4, In the seventh month, on the seventeenth day of the month, the ark rested upon the mountains of Ararat.

Note that from verse 7:11 and 8:4, we see that the span of time extends from the 17th of the second month to the 17th of the seventh month, which is exactly five months. Meanwhile, verse 7:24 and 8:3 equate these same five months with exactly 150 days. The implication is that each month is 30 days (5 months x 30 days/month = 150 days). From this, we derive that the closest thing to a year must be twelve 30-day months, which is 360 days.

Side note: I do not advocate the view (held by some) that in Noah’s day, solar years were actually exactly 360 days, and that solar years have since become longer (now about 365.2422 days). I believe this view is scientifically untenable and theologically unnecessary. However, it is known that 360-day years were used in ancient Mesopotamia, which would be the time and place that Noah lived. References:
It is only natural then that Noah would record months and days according to that calendar, and that Moses would accurately relate Noah’s account. In my view, this is the simplest (and best) explanation.

We see Biblical years more clearly at the opposite end of the Bible. Revelation refers to the great tribulation period two ways: 42 months (Rev 11:2, Rev 13:5) and 1260 days (Rev 11:3, Rev 12:6). The only way to equate 42 months and 1,260 days is to recognize that a year is 360 days, and that it has 12 months with 30 days per month. This corroborates the notion of a Biblical year and Biblical month mentioned in early Genesis (discussed above).

Purpose of Biblical Years

Why does the Bible use two kinds years, with one of them being this simple 360-day “Biblical year“?

  • For normal human purposes, the Bible refers to years based on the Jewish calendar. The Jewish calendar (as well as our modern Gregorian calendar) is more complicated because it’s designed to align with the solar year. This solar alignment is important for agricultural and social purposes.  Using a 360-day year for such purposes would be terrible because seasons would drift. For example, after just 35 years, the winter months would be hot and the summer months would be cold!
  • However, for some prophetic purposes (depending on context), alignment with the solar year is inconsequential! In fact, it would be problematic to base prophecy on a complex calendar system that is dependent on imprecise human efforts to reconcile time with the observed solar year. Reliable prophecy demands a method for measuring time that is both simple and precise, and the 360-day Biblical years are exactly that.

Prophetic Examples

  • The “70 weeks” prophecy in Daniel 9:24-27 is a case where the 360-day years make the most sense, as it measures the precise time between two specific, but distant, events (see The 70th Week of Daniel for more about this prophecy). The book of Daniel focuses mainly on the final 70th “week” (where a “week” represents seven years).
    – We see that this final seven-year period will have a midpoint (Dan 9:27).
    – The period after the midpoint is called “time, times, and half a time” (Dan 7:25, 12:7).
    – This period will feature a wicked ruler persecuting God’s people (Dan 7:25, 12:1).
    – This wicked ruler’s kingdom will finally be destroyed (Dan 7:26).
    – This total period following the midpoint is expressed as 1290 days (Dan 12:11).
    This all makes sense if we recognize that second half of the seven-year period (3 1/2 years) is measured using 360-day years giving 1260 days (360 x 3 1/2) plus one Biblical month (30 days) to account for the destruction of the wicked ruler’s kingdom. This demonstrates that the 70th week refers to seven 360-day years. From this, it follows that all 70 weeks of the prophecy should be measured the same way. This view gains confirmation in the book of Revelation, where we also see a reference to the 1260 days of persecution (Rev 12:6) followed by a period where the earthly kingdom is destroyed (e.g. Rev 19:20-21).
  • The “70 years of captivity” prophecy of Jeremiah (Jer 25:11, 29:10) is a case where the context indicates that the normal Jewish calendar years should be used. We can say this because the 70 years are explained in 2 Chron 36:21, “…to fulfill the word of the LORD by the mouth of Jeremiah, until the land had enjoyed its sabbaths. All the days of its desolation it kept sabbath until seventy years were complete“. The Israelites were supposed to let the land have a “sabbath rest” once every seven years (Lev 25:4), but they neglected this law for 70 sabbath years (i.e. at least 490 years). Moses actually forewarned that such neglect would result in a period of captivity until the due sabbath rest years were repaid (Lev 26:34). Since this prophecy is about sabbath years, and sabbath years are based on the Jewish calendar, it follows that this prophecy should be measured in Jewish calendar years, and not the 360-day years.

To review, we do see two types of years expressed in the Bible. Most of the time, the word “year” refers to the standard Jewish calendar year. However, in prophecy, the context may require that the simpler and more precise 360-day Biblical year is meant instead



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