Age attainment rule: persons born on April first deemed to reach their age on March thirty-first for tax eligibility. The Board clarifies that a person born on 1st April is considered to have attained a particular age on 31st March, the day preceding the anniversary of the birthday; field authorities must apply this criterion in determining senior/very senior citizen eligibility for resident individual taxpayers, relying on the Supreme Court rule that the day of birth is counted as a whole and age is attained on the day before the birthday anniversary, under the Board's powers under section 119.