When a passage references days and nights (e.g. seven days and seven nights), is it to be taken literally as X complete days and X complete nights?

Question

1 Samuel 30:12 KJV - And they gave him a piece of a cake of figs, and two clusters of raisins: and when he had eaten, his spirit came again to him: for he had eaten no bread, nor drunk any water, three days and three nights.

Job 2:13 KJV - So they sat down with him upon the ground seven days and seven nights, and none spake a word unto him: for they saw that his grief was very great.

Jonah 1:7 KJV - Now the LORD had prepared a great fish to swallow up Jonah. And Jonah was in the belly of the fish three days and three nights.

Exodus 24:18 KJV - And Moses went into the midst of the cloud, and gat him up into the mount: and Moses was in the mount forty days and forty nights.

Matthew 12:40 KJV - For as Jonas was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth.

Day = 24 hour period, day = sunlight portion of Day, night = dark portion of Day

It's been said that any portion of a Day is reckoned as a whole Day. Just like for Jesus' duration in the grave, some argue that he did not have to remain in the grave for the duration of 72 hours. Thus, three days and three nights is not a literal expression. Does this same notion apply to other passages that specify X days and X nights?

Answer 1

As noted in the question, the word "day" in the Bible can have ambiguous meaning. It is applied both to the daylight portion of a "day", as well as to the entirety of a day. Whenever hours are referenced, the word "day" will be limited to the 12 daylight hours. But in a case where the word "day" could be taken two ways and the context is insufficient to make the meaning plain, the usage of "days" and "nights," referring to a day's daylight and nighttime portions, is common to clear up any possible ambiguity with reference to the full span of the time.

There is no case of this usage of "day" and "night" or, as in Daniel, "evening" and "morning," where the expression could be reasonably understood to not include a portion of that which is explicitly specified. In other words, if the Bible says "three days and three nights," it means it.

In the case of Jesus, the "sign of Jonas" that Jesus would give is not assigned to the time of his death. Nothing in that prophecy indicates that it applies to death. What the prophecy says is "heart of the earth." Many have misapplied this to the grave--but did Jonah die in the belly of the whale? In fact, it applies to being under the direct control of the kingdom of Rome (kingdoms are represented as beasts in prophecy, of which the whale is one), beginning with Jesus' arrest in the Garden of Gethsemane, and ending with the dispersal of the Roman guard from the tomb when the angel came to resurrect Jesus.

Thursday night: Arrested in the Garden by Romans
Friday (Day): Crucified by Romans
Friday night: In the grave and put under Roman guard
Sabbath (Day): In the grave
Saturday night: In the grave
Sunday (Day): Released from Roman control and resurrected
- - - - - - - - - 
Three days and three nights

One should be careful not to assume the Bible means something different from what it says just because one finds no good application or explanation for it. It is much better to accept it as it reads, then look for the reason(s) it reads in such a peculiar manner as may be observed. The Biblical specification of "days" and "nights" is almost always an indication of a prophetic time. The prophetic significance will be applied to a fairly precise time period, and rounding should never be assumed for time prophecies.