The scenario of the crossing of the Red Sea, incredible though it may seem, corresponds in every detail to the description in the Bible, and brings together all the Exodus passages in a coherent and rational manner. The existence of the Suez sand banks, the tides, and every other detail of natural phenomena all agree perfectly with the narrative. Even the name of the area found immediately beyond the sand banks, "Ayun Musa" (the Moses' wells), corroborates it. And as we will see later, starting from this point all the rest of the itinerary parallels the Bible text exactly. Nearly everything coalesces to confirm exactly what is described in the Bible. There is, however, one particular detail that at first does not seem to fit with this reconstruction, and that is the time of year in which the crossing is believed to have occurred.
According to our reconstruction, the Red Sea crossing took place during a new moon. The departure from Pi-Rameses, fifteen days previously, therefore coincided with a full moon. The Jews traditionally celebrate Easter in memory of that event, coinciding with the first full moon of Spring.
However, by examining the Bible, we can establish with certainty that this tradition is incorrectly based. First of all, we note that the Jewish custom of celebrating Easter, after a long period of suspension, was revived only after they returned from exile in Babylon. During this exile they not only adopted the Aramaic language, but also the Babylonian calendar, which began with the new moon closest to the Spring equinox. Since the Bible stated that Easter was to be celebrated on the fifteenth day of the year (Lev. 23,5; Nm. 9,3-5; 28,16; 33,2; etc.), from that time on Easter was fixed to coincide with the first full moon of Spring.
The Exodus Jews, however, came from Egypt and at the time of the narrated events they almost certainly used the Egyptian calendar, the beginning of which coincides with the flooding of the Nile in June. So the fifteenth day of the year, when they departed from Pi-Rameses, must have been in June (Nm. 33.3).
Various factors support this statement. Some of the events that preceded the Exodus are in fact dated; for example, the seventh plague--the hailstorm--is dated with a maximum margin of error of a week. It occurred when "the flax was blooming and the barley already twilled,” but not yet the wheat (Ex. 9.31-32); clearly this was between the 5th and the 15th April. After this, three more plagues occurred. The Exodus, therefore, took place some time later; it could hardly have happened during the first full moon of Spring. Other biblical indications conflict with a departure at the beginning of Spring, but there is one that puts it definitively in June. It is reliable evidence because it dates from a period very near the events in question, and the Bible states it clearly in the Book of Joshua.
Joshua began the invasion of Palestine during the harvest period (Josh. 3,15; 5,11). In the Jordan Valley today, the grain harvest occurs during the second half of May. Taking into account that nowadays the tendency is to cultivate early varieties and to thresh as early as possible, we are reasonably certain that the harvest in those times did not take place before the end of May. Joshua crossed the Jordan on the tenth day after the beginning of the year (Js. 4,19); five days later he celebrated Easter (Js. 5,10). There can be no doubt--it was in June. Exactly fifteen days later came the recrossing of the Red Sea--at the end of June or at the latest, the beginning of July.
Having established the time of the year in which the Exodus took place, the next step is to discover the precise date. Incredible though it may seem, the Bible itself provides evidence which makes it possible to determine not only the year, but the exact day on which that event--the crossing of the Red Sea so fundamental to the history of the Jewish people and perhaps the most important in all human history--occurred. It all hinges on whether a certain interpretation of the ninth "plague" is exact or not, that is, the three days of "darkness" that fell upon Egypt.
All the so-called plagues refer more or less to extraordinary events that really occurred, but which in some cases are highly exaggerated. Such was the case with the hailstorm (Ex. 9,24-32). The question is how can we interpret these "days of darkness.” The most plausible explanation, the one that seems to be the most sensible, is an eclipse of the sun. This is an event which is quite extraordinary, but not sufficiently so to be defined as a "plague;” to become so, the duration would have to be prolonged to an extreme. In fact it became three days, but here "three" is clearly a period of indeterminate length.
The eclipse plainly occurred when the sun and moon were in conjunction, that is, during a new moon. Since this was after the seventh plague, which occured in April, it must have been the new moon immediately preceding the one at the time the Jews crossed the Red Sea. This puts the time frame at or very close to the end of May.
The interesting thing about eclipses is that the dates can be calculated exactly, even those in very remote history. Therefore, we need only ascertain if in Egypt, in what was most probably the time of the Exodus, there was actually a total eclipse of the sun, and then calculate the exact day. The Jews crossed the Red Sea twenty-nine days later.