How do we know sunset begins Shabbat/Sabbath and Jewish day?

I am a Christian who observes the Sabbath from sunset to sunset. Recently I’ve been made aware of some commentaries and other historical data that claim the Sabbath should be observed beginning at Sunrise. Can you please address the controversy over Genesis 1:3-5 as to what the Hebrew words for evening and morning really mean? Are there some good sources I can look at that would support the sunset to sunset position. Thank you.

Already in the 6 days of creation (Breishit/Genesis 1), the Torah says at the end of every day, “and it was evening and it was morning, day one… the second day… third day, etc. all the way down to “and it was evening and it was morning, the sixth day” and then immediately comes the Sabbath (ibid 2, 1), obviously starting at the following evening. In Judaism, the evening always precedes the morning, and not vice-versa. Regarding that light/day is written before darkness/night (in 1, 3), is irrelevant to your question, for immediately the order is explicit: “and it was evening [=“erev” literally means west, for that’s where the sun is at that time, and only afterwards:] and it was morning”. Similarly, in the classic prayer of Shma (“Hear oh Israel…” Dvarim/Deutoronomy 11, 19; and ibid 6, 7), “And you shall review this [=these words] with your sons… when you go to sleep and when you wake up”. First you recite Shma before you go to sleep and only afterwards, when you wake up, and not vice versa as in western society. So too it's written explicitly regarding Yom Kippur, the “Sabbath of Sabbaths” which again, goes “from evening until evening” (Vayikra/Leviticus 23, 32). BTW, Jews don’t finish the Sabbath exactly at sunset, but rather continue a little longer, to add a little more Sabbath to our lives, and also to “play it safe” (so as not to accidentally do creative-work a little too early) until three average-size stars are seen on Saturday night. I actually could have guessed that you are a Christian, for all Jews are born into this unbroken, non-stop and obvious Jewish tradition and we’ve been doing it this way, from evening until evening and generation to generation, for more than 3,330 years!