TBILLEQ Function

TBILLEQ.js

// Copyright (c) 2012 Sutoiku, Inc. (MIT License)

function TBILLEQ(settlement, maturity, discount) {
  // Return error if either date is invalid
  if (!moment(settlement).isValid() || !moment(maturity).isValid()) return '#VALUE!';

  // Return error if discount is lower than or equal to zero
  if (discount <= 0) return '#NUM!';
  
  // Return error if settlement is greater than maturity
  if (moment(settlement).diff(moment(maturity)) > 0) return '#NUM!';
  
  // Return error if maturity is more than one year after settlement
  if (moment(maturity).diff(moment(settlement), 'years') > 1) return '#NUM!';
  
  // Return bond-equivalent yield
  return (365 * discount) / (360 - discount * DAYS360(settlement, maturity));
}