You will be considered a U.S. resident for tax purposes
if you meet the substantial presence test for the calendar year. To meet
this test, you must be physically present in the United States on at
least:

1. 31 days during the current year, and
2. 183 days during the 3-year period that includes the current year and
   the 2 years immediately before that, counting:
   
   
   • All the days you were present in the current year, and
   • 1/3 of the days you were present in the first year before the
     current year, and
   • 1/6 of the days you were present in the second year before the
     current year.