text: let shortMonths = [
    'jan',
    'feb',
    'mar',
    'apr',
    'may',
    'jun',
    'jul',
    'aug',
    'sep',
    'oct',
    'nov',
    'dec'
  ]
  let longMonths = [
    'january',
    'february',
    'march',
    'april',
    'may',
    'june',
    'july',
    'august',
    'september',
    'october',
    'november',
    'december'
  ]
  
  function buildMapping() {
    const obj = {
      sep: 8 //support this format
    }
    for (let i = 0; i < shortMonths.length; i++) {
      obj[shortMonths[i]] = i
    }
    for (let i = 0; i < longMonths.length; i++) {
      obj[longMonths[i]] = i
    }
    return obj
  }
  
  export function short() { return shortMonths }
  export function long() { return longMonths }
  export function mapping() { return buildMapping() }
  export function set(i18n) {
    shortMonths = i18n.short || shortMonths
    longMonths = i18n.long || longMonths
  }
  