4. December 24, 1952 to November 13, 1986
If, at the time of your birth, both your parents were U.S. citizens and at least one had a prior residence in the United States, you automatically acquired U.S. citizenship with no conditions for retaining it.
If only one parent was a U.S. citizen at the time of your birth, that parent must have resided in the United States for at least ten years, at least five of which had to be after the age of 16. There are no conditions placed on retaining this type of citizenship. If your one U.S. citizen parent is your father and you were born outside of marriage, the same rules apply if your father legally legitimated you before your 21st birthday and you were unmarried at the time. If legitimation occurred after November 14, 1986, your father must have established paternity prior to your 18th birthday, either by acknowledgment or by court order, and must have stated in writing that he would support you financially until your 18th birthday.
The above is from the "Find Law" link previously posted. If this link is true, and these laws clarified the constitution regarding what a natural born citizen is, then Obama was not a "natural born citizen" according to the laws at the time.