Half-year convention
(iii) Half-year convention. The depreciation allowance for a vintage account for which the taxpayer adopts the half-year convention shall be determined by treating all property in the account as placed in service on the first day of the second half of the taxable year and by treating all extraordinary retirements (as defined in paragraph (d)(3)(ii) of this section) from the account as occurring on the first day of the second half of the taxable year. (iv) Rules of application.