years_of_observations
if (increment_overflow(&yearlim, years_of_observations))
if (increment_overflow(&yearlim, years_of_observations))
} else if (years_of_observations <= year - yearbeg)
if (min_year >= ZIC_MIN + years_of_observations)
min_year -= years_of_observations;
if (max_year <= ZIC_MAX - years_of_observations)
max_year += years_of_observations;