That's from 8 USC 1401. If you look at the "notes" tab at the link above, you'll find:
Amendments
1994—Subsec. (h). Pub. L. 103–416 added subsec. (h).
1986—Subsec. (g). Pub. L. 99–653 substituted “five years, at least two” for “ten years, at least five”.
IOW, in August of 1961 the requirement read:
ten years, at least five of which were after attaining the age of fourteen years:>
The change to the law was not retroactive. IOW, Stanley Ann was not eligible to pass on citizenship to Barry, IF he was not born in the US. (Assuming she was married to BHO Sr.).
No person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President; neither shall any Person be eligible to that Office who shall not have attained to the Age of thirty-five Years, and been fourteen Years a Resident within the United States.
ie You can argue whether or not Barry is a natural born citizen, but natural born citizens are not the only class of citizens eligible for POTUS.
Are you saying Barry was a Citizen at the time of the Adoption of the Constitution? That's the only other class of citizens that were eligible to the office of President.
The last President who was a Citizen at the time of the adoption of the Constitution died in 1850 while serving in his second year as President. Zachary Taylor was born in Virginia in 1784, about 4 years before the adoption of the Constitution. He was the 12th President under the Constitution. Some earlier Presidents had been born after the adoption and were natural born citizens. But since him there have been 31 Presidents, 32 if you count The Messaiah, 30 if you don't count him and Chester Arthur. It's quite likely that Chester Arthur was not natural born, but the facts that make that likely were not demonstrated until well after his death. He was born in the US but at the time his father was not a US Citizen, although he became one when Chester was about 14.
Barack H. Obama Sr was never a citizen of the US, nor even a permanent resident alien.
It's arguable that sine he was born in the United States, that Taylor was natural born, and thus fit into both categories. If so, the next previous President who was a citizen at the time of the adoption of the Constitution was William Henry Harrison. He was the 9th President under the Constitution, but unfortunately he died in office of pneumonia, only about a month after taking office.
You are fundamentally misreading the phrasing of the Constitution.
No person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution.....
can be read as:
No person except a natural born Citizen, at the time of the Adoption of this Constitution.....
and or:
No person except a Citizen of the United States, at the time of the Adoption of this Constitution.....
In other words by your logic it is impossible for ANYONE to be a citizen of the US unless they were alive when the Constitution was written.
The proper reading of the clause as written is that there are two cases, two classes of citizens eligible for run for President. This does not include naturalized citizens. Think about it: Previous to the creation of the United States no one was a Citizen of the United States. Everyone was in effect British Citizens. Then one day everyone became citizens. There was no distinction AT THAT TIME between folks born in the US and folks residing in the newly establish US. No place in the Constitution were some rights given to people who had been born say in Maryland prior to the creation of the US and not given to someone who was born in London in say 1740 but who moved to Maryland in 1760.
Actually, it is retroactive.
The full section reads (note bottom):
g) a person born outside the geographical limits of the United
States and its outlying possessions of parents one of whom is an
alien, and the other a citizen of the United States who, prior to
the birth of such person, was physically present in the United
States or its outlying possessions for a period or periods totaling
not less than five years, at least two of which were after attaining
the age of fourteen years: Provided, That any periods of honorable
service in the Armed Forces of the United States, or periods of
employment with the United States Government or with an
international organization as that term is defined in section 288 of
title 22 by such citizen parent, or any periods during which such
citizen parent is physically present abroad as the dependent
unmarried son or daughter and a member of the household of a person
(A) honorably serving with the Armed Forces of the United States, or
(B) employed by the United States Government or an international
organization as defined in section 288 of title 22, may be included
in order to satisfy the physical-presence requirement of this
paragraph. 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