src/deltat.js
function interpolateData (dyear, data) {
  const [fyear, fmonth] = data.firstYM
  const {year, month, first, last} = monthOfYear(dyear)
  const pos = 12 * (year - fyear) + (month - fmonth)
  const table = data.table.slice(pos, pos + 3)
  const d3 = new interp.Len3(first, last, table)
  return d3.interpolateX(dyear)
}
function interpolateData (dyear, data) {
  const [fyear, fmonth] = data.firstYM
  const {year, month, first, last} = monthOfYear(dyear)
  const pos = 12 * (year - fyear) + (month - fmonth)
  const table = data.table.slice(pos, pos + 3)
  const d3 = new interp.Len3(first, last, table)
  return d3.interpolateX(dyear)
}
function interpolateData ( dyear , data ) { const [ fyear , fmonth ] = data . firstYM const { year , month , first , last } = monthOfYear ( dyear ) const pos = 12 * ( year - fyear ) + ( month - fmonth ) const table = data . table . slice ( pos , pos + 3 ) const d3 = new interp . Len3 ( first , last , table ) return d3 . interpolateX ( dyear ) }
interpolation of dataset from finals2000A with is one entry per month
linear interpolation over whole dataset is inaccurate as points per month
are not equidistant. Therefore points are approximated using 2nd diff. interpolation
from current month using the following two points

@private
@param {Number} dyear - julian year
@returns {Number} ΔT in seconds.
interpolation of dataset from finals2000A with is one entry per month linear interpolation over whole dataset is inaccurate as points per month are not equidistant . Therefore points are approximated using 2nd diff . interpolation from current month using the following two points