(a) Whenever in any fiscal year real estate improved in assessed value by over 50 per cent excluding the value of the land by new construction is issued a temporary or permanent occupancy permit after January 1 in any year, the owner of the real estate shall pay a pro rata amount or amounts, as herein defined, to the city or town where such real estate is located that would have been due for the applicable fiscal year under this chapter if the real estate had been so improved on the assessment date for the fiscal year in which the occupancy permit issued. The amounts payable to the city or town shall be determined as follows:

1. (1) A real estate tax based on the assessed value of the improvement for the fiscal year in which such improvement and issuance of an occupancy permit occurred allocable on a pro rata basis to the days remaining in the fiscal year from the date of the issue of the occupancy permit to the end of the fiscal year; and
2. (2) A real estate tax based on the assessed value of the improvement for the succeeding fiscal year where the improvement and issuance of the occupancy permit take place between January 1 and June 30 of any year.