In Massachusetts, the assessment date is January 1st.
The Town of Raynham voters have accepted the following provision:
The assessors of each city and town shall determine the fair cash valuation of such real property for the purpose of taxation on the first day of January of each year. Notwithstanding the foregoing, in any city or town which accepts the provisions of the sentence, buildings and other things erected on or affixed to land during the period beginning on January second and ending on June thirtieth of the fiscal year preceding that to which the tax relates shall be deemed part of such real property as of January first." (MGL, Chapter 59, Section 2A)
In Massachusetts, the fiscal year commences on July 1st and ends the following June 30th. Property taxes are assessed for the fiscal year (July 1 – June 30) based on the value of the property as of the previous January 1st.
For example, property taxes for fiscal year 2018 (July 1, 2017– June 30, 2018) are based on the value of the property as of January 1, 2017.