My friend, the "stanger among us" is referring to a convert to Judaism; it doesn't refer to any "random" stranger spending some time in Israel. Non-Jews are not required to keep the Sabbath; actually, non-Jews are forbidden to keep the Sabbath in all its laws and details. The Sabbath is a special covenant between the Jews and God in which the Jews bear testimony (through their safeguard of the Sabbath) that God created the universe.Sabbath is for YOUR location, YOUR time zone, not Jerusalem's or England's or Fiji's. Why would the artificial "international date line" have any bearing?
Willful sin and unintentional sin are of two different weights, the former far more severe.
If Sabbath was not known before Moses, was the Distinction between clean and unclean animals known before Noah? If God rested on the 7th day of Creation, does that mean he followed his own Sabbath and thus the Sabbath was in place?
Why do you suppose even the gentiles are supposed to obey when in the LAND of Israel? Even the stranger among us in the Holy Land must obey, so its not just purely a Tribal thing. We are the "Light of the nations", meant to teach gentiles the Torah, though Judaism lost its Prosletyzing spirit after the destruction of the Temple.
NOTEWORTHY POINT TO ALL READERS: when the Jews would "proselytize," their intention was not to convert non-Jews to Judaism. Our mission from the inception of our nationhood was to spread the knowledge of One God throughout the world of idolatry and to teach the truths of the Torah to all humanity (that is, to teach the world of the 7 Noahide Laws that God expects every human being to obey, which comes from the Torah). God doesn't want the non-Jews to keep all 613 commandments of the Torah (that is, unless a non-Jew wants to convert by his own free will). The unique thing about Judaism is that, unlike many (if not most) religions, Judaism does not say that if your not a Jew, then you're doomed. God has a place for all people in His world and in the World to Come. Non-Jews can earn a place in the World to Come by doing good deeds and by keeping the 7 Noahide Laws. I think God is pretty fair for only requiring the non-Jews to keep 7 laws, while we Jews have to keep 613.