The purpose of asking for military service dates is to find if our organization has enough "war veteran" members to be able to apply for determination that contributions to the USS Nitro Association will be deductible by donors on their federal tax returns. You are a "war veteran" if you served any time during the dates listed below:

TAX GUIDE "Veterans' Organizations"
IRS Publication 3386
page 37
    
War veterans are defined as persons who have served in the Armed Forces
of the United States during a period of war.  These periods are as follows: 
A. April 21, 1898, through July 4, 1902; 
B. April 6, 1917, through November 11, 1918; 
C. December 7, 1941, through December 31, 1946; 
D. June 27, 1950, through January 31, 1955; 
E. February 28, 1961 through May 7, 1975 in the case of a veteran
who served in the Republic of Vietnam during the period ;
F. August 5, 1964, through May 7, 1975; and          
G. August 2, 1990, and ending on the date prescribed by Presidential
Proclamation or by law.

This page of the publication can be found at the following URL:
http://www.irs.gov/pub/irs-pdf/p3386.pdf