Question: Why does the Sabbath occupy more than one day on the Gregorian Calendar?  Does this not illustrate that the First Dawn After Conjunction Method for reckoning the beginning of the month is wrong?  Shouldn't the world be observing the Sabbaths & Feast Days on the same day?

Answer: You are having an issue here solely because you are forcing the man-mad International Date Line into your equation.  You are trying to unite the entire world on one counterfeit Gregorian day, which necessitates that everyone in the world begin their day according to the International Date Line.  The Creator's Calendar allows the heavenly bodies to determine when a day begins, as opposed to man.  When using the First Dawn After Conjunction method of reckoning, everyone in the entire world will begin their Sabbath within the same 24-hour period; thus, all will be united in observing the same [Biblical] day.  I believe that you are inadvertently looking at this backwards.  Someone has to decide when the day begins, be it Yahuwah, or be it man.  If you wish to unite the entire world on one Gregorian date, then you have no choice but to allow man to tell you when a day begins (via the International Date Line).  The Sabbath, as determined by the FDAC method, occupies only one true day; it is the counterfeit Gregorian calendar that actually reckons two dates where there should be one.

To illustrate this point, here is some homework for you.  Using any reckoning method you wish, try to come up with a scenario in which the entire world can observe one Gregorian date without using the International Date Line.  You will quickly find that it cannot be done. 

It is not an easy thing to wrap our minds around.  But, by Yahuwah's grace, we will achieve a perfect understanding and will break free from all man-made traditions. :)