tranformTimeZone.js

//Accept zoneStr such as '-0400', '-04:00', '0400', '+0400'
//Return such as 4, -4, -4.75, -4.5
function tranformTimeZone(zoneStr) {
  var signSymbol, hours, minutes, zone;

  if (/^\+|-/.test(zoneStr)) {
    signSymbol = zoneStr[0];
    zoneStr = zoneStr.slice(1);
  } else {
    signSymbol = '+';
  }

  if (/:/.test(zoneStr)) {
    hours = zoneStr.split(':')[0];
    minutes = zoneStr.split(':')[1];
  } else {
    hours = zoneStr.slice(0, 2);
    minutes = zoneStr.slice(2,4);
  }

  zone = parseInt(hours) + (parseInt(minutes) / 60);
  if (signSymbol == '-') { zone = -zone }

  return zone;
}