How long was an American draftee during World War II drafted for? I believe is the question you are asking?

Duration of the war plus six months was the term for those drafted during the war. There had been a peacetime draft prior with men serving only a 12 month term, but their enlistments were extended by law to 18 months when they would have begun expiring in fall of 1941, and the duration+6 came about a week after Pearl Harbor.

Have been trying to find the text of the Selective Service Act, but it is harder than you'd think! Since parts are still on the books, all the sites that host US Code show the current, and just mention that sections have expired or been repealed without showing the actual text.

Edit: Because /u/Prufrock451's google-fu trumps mine, here you go:

Original STSA of 1940 text:

Each man inducted under the provisions of subsection (a) shall serve for a training and service period of twelve consecutive months, unless sooner discharged, except that whenever the Congress has declared that the national interest is imperiled, such twelve-month period may be extended by the President to such time as may be necessary in the interests of national defense.

Excerpt from Roosevelt's July, 1941 speech to extend the term of enlistment

Last year the Congress of the United States recognizing the gravity of the world situation held that common prudence required that American defence, at that time relatively very weak, be strengthened in its two aspects. The first called for the production of munitions of all kinds. The second called for the training and service of personnel. The Selective Training and Service Act authorized the annual induction into military service of a maximum of 900,000 men for this training and service, of whom 600,000 are now in the army. The Congress also authorized the induction into service of the National Guard, the reserve officers, and other reserve components of the Army of the United States.

In the absence of further action by the Congress, all of those involved must be released from active service on the expiration of twelve months. This means that beginning this Autumn about two-thirds of the Army of the United States will begin a demobilization.

Still no luck on the December 19, 1941 Revision though.