N.Y. TAX Law § 638

§ 638. New York source income of a part-year resident. (a)\nIndividuals. The New York source income of a part-year resident\nindividual shall be the sum of the following:\n (1) New York adjusted gross income for the period of residence,\ndetermined in accordance with part II of this article as if the\ntaxpayer's taxable year for federal income tax purposes were limited to\nthe period of residence.\n (2) New York source income for the period of nonresidence, determined\nin accordance with section six hundred thirty-one as if the taxpayer's\ntaxable year for federal income tax purposes were limited to the period\nof nonresidence.\n (b) Trusts. The New York source income of a part-year resident trust\nshall be the sum of the following:\n (1) New York adjusted gross income for the period of residence,\ndetermined in accordance with paragraph four of subsection (e) of\nsection six hundred one as if its taxable year for federal income tax\npurposes were limited to the period of residence.\n (2) New York source income for the period of nonresidence, determined\nin accordance with section six hundred thirty-three as if its taxable\nyear for federal income tax purposes were limited to the period of\nnonresidence.\n (c) Stock option grants, stock appreciation rights and restricted\nstock. A part-year resident taxpayer who has been granted statutory\nstock options, restricted stock, nonstatutory stock options or stock\nappreciation rights and who, during such grant period, performs services\nwithin New York for, or is employed within New York by, the corporation\ngranting such option, stock or right, shall compute his or her New York\nsource income as determined under rules and regulations prescribed by\nthe commissioner.\n