Good question, but pay little attention to those who don't know what they are talking about, though it is understandable why there is confusion.
Note, therefore, that there is no symbolic or a minimal symbolic significance to SUNSET in Jewish culture. It is INCIDENTAL to just the SABBATH.
That is, the Jews, like the Egyptians were solar-oriented. So their regular days of the week were counted from NIGHTFALL to NIGHTFALL. That is when they begin their new day. That's why there is all this fuss about trying to determine exactly when that occurs. Some say when three stars can be seen. They used a cloth that was half green and half blue of the same hue of each color. When it was impossible to tell the difference after dusk, then they considered it a new day.
So they thus considered part of the day the remaining sunlight after the sun actually went down. This is reflected by the hours of the day. If the 6th hour was Noon, then the 12th hour was 6 p.m. Hour 1 didn't start until around the time of nightfall at 7 p.m.
Likewise, another huge misconception is that the Jews changed the date at sunset. The did not. They clearly understood the SOLAR CYCLE and applied the CALENDAR DATE to the movement of the sun. Thus, as many will confirm, their "evening" began at noon. That is when the sun began to wane and change course. That is when the sun began to decrease. Sunset was also called "evening". Thus there wree TWO EVENINGS. They broke up their day into periods of "watches" which were 3 hours each. So this period between noon and sunset was a period of two watches, the second watch being simply called "between the two evenings" which is a reference to 3 p.m.
Likewise, as we do, they had two "mornings." One that began at midnight, signaling when the sun changed course and began to increase again, and when the sun actually was seen over the horizon. So very NATURAL observations.
It only gets complex with the SABBATH. The sabbath was special day and it simply began earlier than the regular day. It included the common evening meal, so that the sabbath day began and ended with a common meal. Here you must please note, threfore, that the Jews might begin the sabbath at sundown, but it is not until nightfall that they light that candle that begins the next day. They are very, very, very specific about the separation of the holy and profane. When the official holy day of the sabbath ends and the next day when they can work, begins. But this is NOT at sunset. That candle is lit at the time of nightfall.
So therefore, the Sabbath day is a bit longer than regular days, which are from nightfall to nightfall. The sabbath day is from sunset to nightfall. So this is your rare OPPORTUNITY to ERASE FROM YOUR MIND this "sunset to sunset" concept, which is just erroneous presumption that became an ingrained concept. It's not accurate.
Weekday: Nightfall to nightfall.
Sabbath: Sunset to nightfall.
Preparation: Nightfall to sunset.
Because of the above, clearly, there is no specific symbolic meaning attached to sundown, in my opinion. It's only incidental, and actually an EXCEPTION to their concept of either the weekday beginning at nightfall or the calendar day that begins and ends at midnight.
SUNSET is not as significant as nghtfall or midnight/noon, IMHO as far as symbolic reference.
In that regard, Christ, who is represented by the sun, becomes flesh around the time of the winter solstice, that is about 3 days after the technical solstice. I know paganism and Mithraism recognize the same thing. But if you check Volume 6 of "Studies in the Scriptures" they understood that December 25th was the date of ANNUNCIATION to Mary that she was pregnant. That was the precise "instance" of when the spirit being in heaven that was the Christ actually became flesh. So there is a connection with Christ of the solar cycle. He was born in the fall 9 months later. But he actually BECAME FLESH at the time the visible return of the sun began 3-4 days after the solstice, which occurs on December 21st.
Same thing happened at the second coming in 1992 on December 25-26th. So the instance of when Christ leaves heaven and takes up flesh of mankind again, is in relation to the sun, which I only mention because it underscores as far as Biblical symbolism, a more intellectual cosmological understanding of the solar cycle with respect to the earth's orbit around the sun, and not the rotation of the earth that creates sunsets.
But that's understandable, because, actually, the solstice is a specific relationship between the earth's ORBIT and not ROTATION. Sunset relects ROTATION, not orbit. So the solstice is experienced by everyone on the planet in relation to the sun at the same time. But at any given second someone on the earth is experiencing sunrise or sunset.
I have this saying to flatter friends sometimes that: "You know, the sun doesn't rise until you open your eyes in the morning!" Of course, I don't tell them WHERE it rises! But it's true, because somewhere in that instant, the sun does rise.
So considering that, in the general BIG picture, the sunset/sunrise are not big issues of symbolism that I can see as far as the Bible or even Jewish culture.
Also, even though it has been commented that it might be confusing as far as the Bible is concerned over the solar versus other concepts, it might be detailed and sublte but you can determine from the Bible by comparison precisely all the above I've mentioned. Only some people refuse to accept the obvious because they have their own needs to be fulfilled.
Case in point JWs! Now it is clear that the same night passover is eaten that the Jews left Egypt. They were to celebrate the day/night they left Egypt with a special sabbath. That sabbath day of celebration is the first day of unfermented cakes. Of course, all sabbath days begin at sunset, so the 1st day of unfermented cakes begins at sunset as well, in the "evening." BUT, because the Jews didn't change the date officially until midnight, the 1st day of unfermented cakes is said by the Bible to begin on the 14th in the evening. Though the Jews left Egypt on the 15th of Nisan. But that's only because they left after midnight. But it was the SAME NIGHT as Passover.
But JWs need Jesus to die on Nisan 14th regardless. So to tell them the date changed at midnight is something they refuse to hear. They can't accept it. They need to change the date at sundown so that Jesus dies on Nisan 14th at 3 pm on sundown. This completely ignores that passover is eaten the same day the Jews leave Egypt which makes it a sabbath day. Nisan 14th is a preparation day. Jesus DOES INDEED die on a preparation day, but preparation of Nisan 14th ended at sundown.
Thus the same night passover is eaten is the same 15th night the Jews leave Egypt. That means it was the 15th when Jesus was arrested, plain and simple. It was not a preparation day. Passover is a sabbath day, the 1st day of unfermented cakes. Period. Jews celebrate it that way, but Christians, needing to have Jesus specifically fulfill being the passover lamb have to kill him somehow in some way on the 14th, regardless. That is such a visual fulfillment for them, I understand, but it contradicts all the facts.
Now this is complicated because you have very educated and intellectual persons, knowledgeable persons who comment academically on these things and they can't grasp it either. That is, the REFUSE to face the obvious themselves. The fact is, Passover is eaten on a sabbath day, since that same night is celebrated as a special sabbath related to their leaving Egypt that night. It's sooo simple. But the idea that Jesus died later that week and not that same night simply is something they cannot accept. Combine that with the common focus on Jews beginning their day at "sunset" because of the sabbath, and it is impossible to convince them of anything and they remain CONFUSED.
But now YOU are not confused. You have the goods. You have a good question. I hope this has been helpful.
Cheerio.
JC