# datefix: convert mm/dd/yy into yyyy-mm-dd (for 1940 to 2039)

awk '
function datefix(s,   y, date) {
  split(s, date, "/")
  y = date[3]<40 ? 2000+date[3] : 1900+date[3]  # arbitrary year
  return sprintf("%4d-%02d-%02d", y, date[1], date[2])
}

{ print(datefix($0)) }
' $*
