num2shortmonth() #@ Convert number to abbreviated month name
{                #@ USAGE: num2month MONTHNUMBER [VAR]
  local _num=${1#0} _var=$2
  local _months=( '' Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec )
  local _name=${_months[_num]}

  is_var "$_var" &&
    printf -v "$_var" %s "$_name" ||
      printf '%s\n' "$_name"
}