When the Bible speaks of 3 1/2 years how do we know it means 3 1/2 years as the Bible also says a day is as a thousand years. How do we determine time in the Bible?
In one place (2 Peter 3:8) the Bible says, “With the Lord, a day is like 1,000 years and 1,000 years is like a day.”
This was not meant as general rule in viewing time in the Bible. Peter was describing the way the Lord looks at time, and it goes both ways. For Him, 1,000 years could pass as if it was no more than a day to us, and a day to Him could last for 1,000 years as we reckon time.
But we are not God. For us time is not elastic. Therefore unless we are clearly directed to do otherwise, we’re supposed to reckon time by human standards.
The most frequent mention of a 3 1/2 year period of time in the Bible refers to the Great Tribulation. It is also described as being 42 months long (Rev. 11:2), and 1260 days long (Rev. 12:6). This leaves no doubt as to the Great Tribulation’s duration.