1986 is apparently the year of the amendment to Sec. 1401(g) which governs Obama's citizenship. However if you will look in the footnotes to the statue, you will see that it applies only to persons born after November, 1986 and thus the reduction of term of residence for the single parent citizen from 5 to 2 is inapplicable to Obama.
Thus if he was born in Kenya, he is not only not eligible to serve as President under Article II, Sec. 1, Par. 4, he is also not a citizen of the United States.
IANAL, but I think that the footnote and the actual USC language refer to it taking effect October 1988, with the provision of it applying to those born after November 1986.
Note that (g) itself states: "This proviso shall be applicable to persons born on or after December 24, 1952, to the same extent as if it had become effective in its present form on that date;"
If this wasn't to go into effect for people born before 1986, why would the military proviso be referenced with such an old date?
From what I see, it's retroactive to all....with a 2 years/14-years clause that would make Sen. Obama a natural born citizen if he was born in Hawaii.