code: function formatTimezoneOffset (minutes) {
    let sign = simpleSign(negateExceptForZero(minutes))
    minutes = Math.abs(minutes)
    let hours = Math.floor(minutes / 60)
    minutes -= hours * 60
    let strHours = String(hours)
    let strMinutes = String(minutes)
    if (strHours.length < 2) strHours = '0' + strHours
    if (strMinutes.length < 2) strMinutes = '0' + strMinutes
    return (sign === -1 ? '-' : '+') + strHours + strMinutes
  }
docs: The amount of effort that went into crafting these cases to handle -0 (just so we don't lose that information when parsing and reconstructing) but can also default to +0 was extraordinary.