For forty days and forty nights it rained in the
desert, while
Noah was in the
ark...
Jesus walked the
desert for forty days and forty nights. (
Lent is 40 days long).
In many parts of the Judeo-Christian
Bible, the length of time
forty days and forty nights is mentioned again and again.
Modern theologians believe that forty days and forty nights was not a set
length of time but a
storytelling convention. It is believed that the idea of "forty days and forty nights" really meant "a long length of time that no one really kept
track of". This is to keep
story accuracy, without worrying about the
minute details of actual numbers, where they didn't matter.
It also made stories easy to
remember. For generations, the
Bible was not written down many times, and thus vague generalizations made it much easier to remember the
stories. You will notice the number forty in the bible many times, in other places, not for a
length of time. It stands for simply "
a long time", or "
a large amount". In stories such as "
The Forty Martyrs", it is not simply a weird conincidence that there are forty people killed. It is simply meant that a lot of people died that day, so many that people didn't really keep track of it.
Typically you will not find these generalizations in the "well kept" parts of the bible:
Hebrew Law and the Letters to (X). These were well kept, and well studied (and started off written down). The more "vague" portions of the Bible (
Genesis, the early
Hebrew Books, non-Biblical accounts of early
Christianity) are more likely to have this sort of
generalization, as they were more story than
scripture for a long time.