Before, during, and after World War II, the United States held eight draft registrations;

Registration	Date	Birth dates	Note
1	October 16, 1940	October 17, 1904-October 16, 1919	Men 21-35 years old
2	July 1, 1941	October 17, 1919-July 1, 1920	Men who had turned 21 since the last registration, and men who were of age but had failed to register in the first registration
3	February 16, 1942	February 17, 1897-October 16, 1904 and July 2, 1920-December 31, 1921	Men 20-21 and 37-44 years old
4	April 27, 1942	April 28, 1877-February 16, 1897	Men 45-64 years old (not liable for military service)
5	June 30, 1942	January 1, 1922-June 30, 1924	Applicable 18 year old men
6 (I)	December 11-17, 1942	July 1-August 31, 1924	" "
6 (I)	December 18-24, 1942	September 1-October 31, 1924	" "
6 (I)	December 26-31, 1942	November 1-December 31, 1924	" "
6 (II)	January 1, 1943-March 31, 1947	January 1, 1925-March 31, 1929	By law, men were to register as soon as possible on or after they turned 18 years old
Extra	November 16-December 31, 1943	January 1, 1899-December 31, 1925	Men 18-44 years old living abroad. Beginning on January 1, 1944, by law, men were to register as soon as possible on or after they turned 18 years old
Special	October 23-31, 1944	November 1, 1899-October 31, 1926	Men 18-44 years old living in the US Virgin Islands. Beginning on November 1, 1944, by law, men were to register as soon as possible on or after they turned 18 years old

Common to all the draft registrations, except the fourth one, the D.S.S. Form 40 (an eight-page general questionnaire) and the D.S.S. Form 311 (an occupational and census-like questionnaire) was mailed to each registrant, to be completed and returned to sender within ten days. After these forms were received, each registrant received the D.S.S. Form 201, a notice to report for a physical and mental examination. After the examination was completed, all registrants, irrespective of whether they had been accepted, rejected or were not liable for military service due to advanced age, received the D.S.S. Form 2, or draft registration card, which provided proof of registration and had to be carried on one's person at all times. After examinations had been processed, each registrant, except those who were 45-64 years old, received the D.S.S. Form 57, a notice of classification that also contained, if applicable, the man's draft order number.

Sources:

Army Selectee's Handbook For Those Men Who Will Be Called For Duty under the Selective Training and Service Act, by John R. Craf, First Lieutenant Q.M.C., Army of the United States

Registration and Selective Service (Selective Service System Special Monograph no. 4, 1946; Government Printing Office)