Convert 'Wednesday, October 10, 2012' to '20121010'

format-date.xquery

declare function local:format-date($date as xs:string)
{
  format-date(
    local:string-to-date(substring-after($date, ", ")),
    "[Y][M][D]"
  )
};

declare function local:string-to-date($date as xs:string) as xs:date
{
  let $month-name := substring-before($date, " ")
  let $day := substring-before(substring-after($date, " "), ",")
  let $year := substring-after($date, ", ")

  let $month := local:month-name-to-number($month-name)
   
  return xs:date(concat($year, "-", $month, "-", $day))
};

declare function local:month-name-to-number($month-name as xs:string)
{
  switch($month-name)
  case "January" return "01"
  case "February" return "02"
  case "March" return "03"
  case "April" return "04"
  case "May" return "05"
  case "June" return "06"
  case "July" return "07"
  case "August" return "08"
  case "September" return "09"
  case "October" return "10"
  case "November" return "11"
  case "December" return "12"
  default return error(xs:QName("FOO"), "Wrong Month name")
};

local:format-date("Wednesday, October 10, 2012") (: output: 20121010 :)