function toIMFDate (date) {
  if (typeof date === 'number') {
    date = new Date(date)
  }

  return `${IMFDays[date.getUTCDay()]}, ${IMFPaddedNumbers[date.getUTCDate()]} ${IMFMonths[date.getUTCMonth()]} ${date.getUTCFullYear()} ${IMFPaddedNumbers[date.getUTCHours()]}:${IMFPaddedNumbers[date.getUTCMinutes()]}:${IMFPaddedNumbers[date.getUTCSeconds()]} GMT`
}
@see https://www.rfc-editor.org/rfc/rfc7231#section-7.1.1.1
@param {number|Date} date
  IMF-fixdate  = day-name "," SP date1 SP time-of-day SP GMT
  ; fixed length/zone/capitalization subset of the format
  ; see Section 3.3 of [RFC5322]

  day-name     = %x4D.6F.6E ; "Mon", case-sensitive
              / %x54.75.65 ; "Tue", case-sensitive
              / %x57.65.64 ; "Wed", case-sensitive
              / %x54.68.75 ; "Thu", case-sensitive
              / %x46.72.69 ; "Fri", case-sensitive
              / %x53.61.74 ; "Sat", case-sensitive
              / %x53.75.6E ; "Sun", case-sensitive
  date1        = day SP month SP year
                  ; e.g., 02 Jun 1982

  day          = 2DIGIT
  month        = %x4A.61.6E ; "Jan", case-sensitive
              / %x46.65.62 ; "Feb", case-sensitive
              / %x4D.61.72 ; "Mar", case-sensitive
              / %x41.70.72 ; "Apr", case-sensitive
              / %x4D.61.79 ; "May", case-sensitive
              / %x4A.75.6E ; "Jun", case-sensitive
              / %x4A.75.6C ; "Jul", case-sensitive
              / %x41.75.67 ; "Aug", case-sensitive
              / %x53.65.70 ; "Sep", case-sensitive
              / %x4F.63.74 ; "Oct", case-sensitive
              / %x4E.6F.76 ; "Nov", case-sensitive
              / %x44.65.63 ; "Dec", case-sensitive
  year         = 4DIGIT

  GMT          = %x47.4D.54 ; "GMT", case-sensitive

  time-of-day  = hour ":" minute ":" second
              ; 00:00:00 - 23:59:60 (leap second)

  hour         = 2DIGIT
  minute       = 2DIGIT
  second       = 2DIGIT