SECTION 1. Section thirty-six of Republic Act Numbered One hundred and eighty-three is hereby amended to read as follows:
"SEC. 36. When assessment may be increased or reduced.&mdashThe City Assessor shall during the first fifteen days of January of each year add to his list of taxable real estate in the city the value of the improvements placed upon such property during the preceding year, and any property which is taxable and which has theretofore escaped taxation. He may during the same period revise and correct the assessed value of any or all parcels of real estate in the city which are not assessed at their true money value, by reducing or increasing the existing assessment as the case may be once every three years."