src/deltat.js
function interpolate (dyear, data) {
  const d3 = interp.len3ForInterpolateX(dyear,
    data.first, data.last, data.table
  )
  return d3.interpolateX(dyear)
}
function interpolate (dyear, data) {
  const d3 = interp.len3ForInterpolateX(dyear,
    data.first, data.last, data.table
  )
  return d3.interpolateX(dyear)
}
function interpolate ( dyear , data ) { const d3 = interp . len3ForInterpolateX ( dyear , data . first , data . last , data . table ) return d3 . interpolateX ( dyear ) }
interpolation of dataset
@private
@param {Number} dyear - julian year
@returns {Number} ΔT in seconds.
interpolation of dataset