2. Citizenship Time Requirements: The statute (the letter of the law) provides that in order to file a naturalization petition, the applicant must be:  

a. A  Lawful Permanent Resident, (LPR),  i.e.., green card holder 
    (exception if served in war for the U.S.),   

b. 18 years or older (unless military involvement),   

c. Resident continuously for 5 years (employment based)  subsequent to
   LPR; status. If married to US citizen (USC) the residency requirement
   only 3 years but there are several conditions to the latter 3 year rule
  (e.g. parties  must have been married for at least 3 years, no legal
   separation, etc.)   

d. Must reside in the state in which petition is filed for at least 3 months.   

e. Must be physically present in the US for at least one half of the 5 years
    (or one half of the 3 years in case spouse is USC).   

f. Must not be absent from the US for a continuous period of more than 1
   year during the period for  which continuous residence is required.
   Absence of more than 6 months but less than 1 year establishes the
   presumption of not satisfying the continuity of residence, that can be
   rebutted.