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