Verse 13 shows a complete day and a complete night with its next morning. With this usage, it clearly establishes right within the context of Passover and the Days of Unleavened Bread, that there is a difference between "night" and "morning"—between lailah and boqer. The locusts arrived at boqer (morning). Did you notice? Boqer follows lailah.
Even as ben ha arbayim follows ba erev, boqer follows lailah. When that occurs, naturally, they have to butt up against one another. But it is very clearly established that they are NOT the same things. They are NOT "night" and "morning" at the same time.
It does not say that the locusts arrived shortly after midnight. This is the argument of the proponents of a fifteenth Passover. They say that boqer arrives right after midnight. But it is still pitch dark right after midnight. It is still night. It is still lailah. Lailah and boqer are not the same thing—established by Genesis 1, Exodus 10, and (as we are going to see) other Scriptures as well.
