First, let me mention that it sure looks like months for Israel started on new moons:

I Samuel 20:18 Then Jonathan said to David, To morrow is the new moon: and thou shalt be missed, because thy seat will be empty.

 24 ¶ So David hid himself in the field: and when the new moon was come, the king sat him down to eat meat.

 27 And it came to pass on the morrow, which was the second day of the month, that David’s place was empty: and Saul said unto Jonathan his son, Wherefore cometh not the son of Jesse to meat, neither yesterday, nor to day?

The three lines above would show that the second day of the month was the day after the new moon, that the month began with the new moon.

Also then, Passover was to be had on the 14th day of the first month:

Leviticus 23:5 In the fourteenth day of the first month at even is the LORD’S passover.

That would mean that Passover was at the full moon of the first month.

Also, lunar eclipses happen on full moons, not solar eclipses.

Solar eclipses happen on new moons.

So why have some been teaching, lately, that there was a solar eclipse during the crucifixion, which was at Passover?

Also, the darkness from solar eclipses don't last for three hours.

Also some are claiming that Nineveh repented at a solar eclipse?

How do they know the date when Jonah preached there, or the date when Nineveh repented?

Did they assume, first, that Nineveh, instead of being convicted by the preaching, instead got scared of an eclipse?

Then did they lookup when solar eclipses happened in the Nineveh area, and then picked the one closest to the time scholars say Jonah lived?

Then did they begin to teach that Nineveh repented because of an eclipse?

There are other eclipses brought up, as well, but no need to belabor the point.

What I really wanted, was to ask a question about what Zechariah is referring to:

Zechariah 14:6 And it shall come to pass in that day, that the light shall not be clear, nor dark:

 7 But it shall be one day which shall be known to the LORD, not day, nor night: but it shall come to pass, that at evening time it shall be light.

What is that talking about?

What does it mean that, "the light shall not be clear"?

Even more perplexing, what does it mean that, "the light shall not be dark"?

It does not say an absence of darkness, but that the light shall not be dark.

Conversely then, what is light that is dark?

Also, what is a day, where simultaneously it is both not day nor night?

It does not say that it will be both day and night, as on two parts of the earth at the same time.

No, it says, "not day, nor night".

So, what is it when the light is both not clear and not dark, and the day is both not day nor night?

Please help me to understand this.

My thought is that it is not something brushed away by simply appealing to Hebrew grammar or syntax.

Rather that this is to be a special sign to the Jews at the return of Jesus, a sign that has not ever happened before.

So, please, what is Zechariah referring to?