diff --git a/bin/ikarus b/bin/ikarus
index 2012bf6..4f08424 100755
Binary files a/bin/ikarus and b/bin/ikarus differ
diff --git a/bin/ikarus-runtime.c b/bin/ikarus-runtime.c
index 2e11127..13e00b0 100644
--- a/bin/ikarus-runtime.c
+++ b/bin/ikarus-runtime.c
@@ -773,6 +773,29 @@ ikrt_strftime(ikp outstr, ikp fmtstr){
   return fix(rv);
 }
 
+ikp
+ikrt_bvftime(ikp outbv, ikp fmtbv){
+  time_t t;
+  struct tm* tmp;
+  t = time(NULL);
+  tmp = localtime(&t);
+  if(tmp == NULL){
+    fprintf(stderr, "Error in time: %s\n", strerror(errno));
+  }
+  int rv = 
+    strftime((char*)outbv+off_bytevector_data,
+             unfix(ref(outbv, off_bytevector_length)) + 1,
+             (char*)fmtbv+off_bytevector_data,
+             tmp);
+  if(rv == 0){
+    fprintf(stderr, "Error in strftime: %s\n", strerror(errno));
+  }
+  return fix(rv);
+}
+
+
+
+
 ikp
 ikrt_close_file(ikp fd, ikpcb* pcb){
   int err = close(unfix(fd));
diff --git a/src/ikarus.boot b/src/ikarus.boot
index caf8f53..4f17c54 100644
Binary files a/src/ikarus.boot and b/src/ikarus.boot differ
diff --git a/src/ikarus.compiler.ss b/src/ikarus.compiler.ss
index f559d41..77db7b7 100644
--- a/src/ikarus.compiler.ss
+++ b/src/ikarus.compiler.ss
@@ -1943,7 +1943,7 @@
         $fx= $fx< $fx<= $fx> $fx>= $fxquotient $fxmodulo $fxsll $fxsra $fxlogxor $exit) 
        (andmap (check op fixnum?) rand*)]
       [($fixnum->char) 
-       (andmap (check op byte?) rand*)]
+       (andmap (check op fixnum?) rand*)]
       [($char->fixnum $char= $char< $char<= $char> $char>= $string)
        (andmap (check op char?) rand*)]
       [($make-vector $make-string)
diff --git a/src/ikarus.intel-assembler.ss b/src/ikarus.intel-assembler.ss
index 113448c..62d0cfa 100644
--- a/src/ikarus.intel-assembler.ss
+++ b/src/ikarus.intel-assembler.ss
@@ -868,6 +868,8 @@
            (vector-set! vec (fx+ reloc-idx 1) v)
            (set! reloc-idx (fx+ reloc-idx 2))]
           [(foreign-label)
+           ;;; FIXME: converted strings should be memoized.
+           ;;;        wait for equal? hash tables.
            (let ([name 
                   (if (string? v)
                       (string->utf8-bytevector v)
diff --git a/src/ikarus.transcoders.ss b/src/ikarus.transcoders.ss
index aca8ade..c7db14d 100644
--- a/src/ikarus.transcoders.ss
+++ b/src/ikarus.transcoders.ss
@@ -1,14 +1,12 @@
 
 (library (ikarus transcoders)
   (export string->utf8-bytevector
-          #;utf8-bytevector->string)
-  (import (except (ikarus) string->utf8-bytevector)
+          utf8-bytevector->string)
+  (import (except (ikarus) string->utf8-bytevector utf8-bytevector->string)
           (ikarus system $strings)
           (ikarus system $bytevectors)
           (ikarus system $fx)
-          (ikarus system $chars)
-          )
-
+          (ikarus system $chars)) 
   ;;; From http://en.wikipedia.org/wiki/UTF-8
   ;;; hexadecimal      binary scalar value            UTF8
   ;;; 000000-00007F    00000000_00000000_0zzzzzzz     0zzzzzzz
@@ -24,71 +22,230 @@
   ;;; replace: places a U+FFFD in place of the malformed bytes
   ;;; raise: raises an error
 
-  (define (utf8-string-size str)
-    (let f ([str str] [i 0] [j ($string-length str)] [n 0])
-      (cond
-        [($fx= i j) n]
-        [else
-         (let ([c ($string-ref str i)])
-           (let ([b ($char->fixnum c)])
-             (f str ($fxadd1 i) j
-                ($fx+ n
-                  (cond
-                    [($fx<= b #x7F)    1]
-                    [($fx<= b #x7FF)   2]
-                    [($fx<= b #xFFFF)  3]
-                    [else              4])))))])))
-
-  (define (fill-utf8-bytevector bv str)
-    (let f ([bv bv] [str str] [i 0] [j 0] [n ($string-length str)])
-      (cond
-        [($fx= i n) bv]
-        [else
-         (let ([c ($string-ref str i)])
-           (let ([b ($char->fixnum c)])
-             (cond
-              [($fx<= b #x7F)
-               ($bytevector-set! bv j b)
-               (f bv str ($fxadd1 i) ($fxadd1 j) n)]
-              [($fx<= b #x7FF)  
-               ($bytevector-set! bv j
-                 ($fxlogor #b11000000 ($fxsra b 6)))
-               ($bytevector-set! bv ($fx+ j 1)
-                 ($fxlogor #b10000000 ($fxlogand b #b111111)))
-               (f bv str ($fxadd1 i) ($fx+ j 2) n)]
-              [($fx<= b #xFFFF) 
-               ($bytevector-set! bv j
-                 ($fxlogor #b11100000 ($fxsra b 12)))
-               ($bytevector-set! bv ($fx+ j 1)
-                 ($fxlogor #b10000000 ($fxlogand ($fxsra b 6) #b111111)))
-               ($bytevector-set! bv ($fx+ j 2)
-                 ($fxlogor #b10000000 ($fxlogand b #b111111)))
-               (f bv str ($fxadd1 i) ($fx+ j 3) n)]
-              [else
-               ($bytevector-set! bv j
-                 ($fxlogor #b11110000 ($fxsra b 18)))
-               ($bytevector-set! bv ($fx+ j 1)
-                 ($fxlogor #b10000000 ($fxlogand ($fxsra b 12) #b111111)))
-               ($bytevector-set! bv ($fx+ j 2)
-                 ($fxlogor #b10000000 ($fxlogand ($fxsra b 6) #b111111)))
-               ($bytevector-set! bv ($fx+ j 3)
-                 ($fxlogor #b10000000 ($fxlogand b #b111111)))
-               (f bv str ($fxadd1 i) ($fx+ j 4) n)])))])))
-
-
   (define string->utf8-bytevector
     (lambda (str)
+      (define (utf8-string-size str)
+        (let f ([str str] [i 0] [j ($string-length str)] [n 0])
+          (cond
+            [($fx= i j) n]
+            [else
+             (let ([c ($string-ref str i)])
+               (let ([b ($char->fixnum c)])
+                 (f str ($fxadd1 i) j
+                    ($fx+ n
+                      (cond
+                        [($fx<= b #x7F)    1]
+                        [($fx<= b #x7FF)   2]
+                        [($fx<= b #xFFFF)  3]
+                        [else              4])))))])))
+      (define (fill-utf8-bytevector bv str)
+        (let f ([bv bv] [str str] [i 0] [j 0] [n ($string-length str)])
+          (cond
+            [($fx= i n) bv]
+            [else
+             (let ([c ($string-ref str i)])
+               (let ([b ($char->fixnum c)])
+                 (cond
+                  [($fx<= b #x7F)
+                   ($bytevector-set! bv j b)
+                   (f bv str ($fxadd1 i) ($fxadd1 j) n)]
+                  [($fx<= b #x7FF)  
+                   ($bytevector-set! bv j
+                     ($fxlogor #b11000000 ($fxsra b 6)))
+                   ($bytevector-set! bv ($fx+ j 1)
+                     ($fxlogor #b10000000 ($fxlogand b #b111111)))
+                   (f bv str ($fxadd1 i) ($fx+ j 2) n)]
+                  [($fx<= b #xFFFF) 
+                   ($bytevector-set! bv j
+                     ($fxlogor #b11100000 ($fxsra b 12)))
+                   ($bytevector-set! bv ($fx+ j 1)
+                     ($fxlogor #b10000000 ($fxlogand ($fxsra b 6) #b111111)))
+                   ($bytevector-set! bv ($fx+ j 2)
+                     ($fxlogor #b10000000 ($fxlogand b #b111111)))
+                   (f bv str ($fxadd1 i) ($fx+ j 3) n)]
+                  [else
+                   ($bytevector-set! bv j
+                     ($fxlogor #b11110000 ($fxsra b 18)))
+                   ($bytevector-set! bv ($fx+ j 1)
+                     ($fxlogor #b10000000 ($fxlogand ($fxsra b 12) #b111111)))
+                   ($bytevector-set! bv ($fx+ j 2)
+                     ($fxlogor #b10000000 ($fxlogand ($fxsra b 6) #b111111)))
+                   ($bytevector-set! bv ($fx+ j 3)
+                     ($fxlogor #b10000000 ($fxlogand b #b111111)))
+                   (f bv str ($fxadd1 i) ($fx+ j 4) n)])))])))
       (unless (string? str) 
         (error 'string->utf8-bytevector "~s is not a string" str))
       (fill-utf8-bytevector
         ($make-bytevector (utf8-string-size str))
         str)))
 
+  (define utf8-bytevector->string
+    (let ()
+      (define who 'utf8-bytevector->string)
+      (define (count bv mode)
+        (let f ([x bv] [i 0] [j ($bytevector-length bv)] [n 0] [mode mode])
+          (cond
+            [($fx= i j) n]
+            [else
+             (let ([b0 ($bytevector-u8-ref x i)])
+               (cond
+                 [($fx<= b0 #x7F) 
+                  (f x ($fxadd1 i) j ($fxadd1 n) mode)]
+                 [($fx= ($fxsra b0 5) #b110)
+                  (let ([i ($fxadd1 i)])
+                    (cond
+                      [($fx< i j) 
+                       (let ([b1 ($bytevector-u8-ref x i)])
+                         (cond
+                           [($fx= ($fxsra b1 6) #b10) 
+                            (f x ($fxadd1 i) j ($fxadd1 n) mode)]
+                           [(eq? mode 'ignore) 
+                            (f x i j n mode)]
+                           [(eq? mode 'replace) 
+                            (f x i j ($fxadd1 n) mode)]
+                           [else
+                            (error who "invalid byte sequence ~s ~s" b0 b1)]))]
+                      [(eq? mode 'ignore) n]
+                      [(eq? mode 'replace) ($fxadd1 n)]
+                      [else
+                       (error who "invalid byte ~s near end of bytevector" b0)]))]
+                 [($fx= ($fxsra b0 4) #b1110)
+                  (cond
+                    [($fx< ($fx+ i 2) j) 
+                     (let ([b1 ($bytevector-u8-ref x ($fx+ i 1))]
+                           [b2 ($bytevector-u8-ref x ($fx+ i 2))])
+                       (cond
+                         [($fx= ($fxsra ($fxlogor b1 b2) 6) #b10)
+                          (f x ($fx+ i 3) j ($fxadd1 n) mode)]
+                         [(eq? mode 'ignore) 
+                          (f x ($fxadd1 i) j n mode)]
+                         [(eq? mode 'replace)
+                          (f x ($fxadd1 i) j ($fxadd1 n) mode)]
+                         [else (error who "invalid sequence ~s ~s ~s" b0 b1 b2)]))]
+                    [(eq? mode 'ignore) (f x ($fxadd1 i) j n mode)]
+                    [(eq? mode 'replace) (f x ($fxadd1 i) j ($fxadd1 n) mode)]
+                    [else (error who "incomplete char sequence")])]
+                 [($fx= ($fxsra b0 3) #b11110)
+                  (cond
+                    [($fx< ($fx+ i 3) j) 
+                     (let ([b1 ($bytevector-u8-ref x ($fx+ i 1))]
+                           [b2 ($bytevector-u8-ref x ($fx+ i 2))]
+                           [b3 ($bytevector-u8-ref x ($fx+ i 3))])
+                       (cond
+                         [($fx= ($fxsra ($fxlogor b1 ($fxlogor b2 b3)) 6) #b10)
+                          (f x ($fx+ i 4) j ($fxadd1 n) mode)]
+                         [(eq? mode 'ignore) 
+                          (f x ($fxadd1 i) j n mode)]
+                         [(eq? mode 'replace)
+                          (f x ($fxadd1 i) j ($fxadd1 n) mode)]
+                         [else (error who "invalid sequence ~s ~s ~s ~s" b0 b1 b2 b3)]))]
+                    [(eq? mode 'ignore) (f x ($fxadd1 i) j n mode)]
+                    [(eq? mode 'replace) (f x ($fxadd1 i) j ($fxadd1 n) mode)]
+                    [else (error who "incomplete char sequence")])]
+                 [(eq? mode 'ignore) (f x ($fxadd1 i) j n mode)]
+                 [(eq? mode 'replace) (f x ($fxadd1 i) j ($fxadd1 n) mode)]
+                 [else (error who "invalid byte ~s" b0)]))])))
+      (define (fill str bv mode)
+        (let f ([str str] [x bv] [i 0] [j ($bytevector-length bv)] [n 0] [mode mode])
+          (cond
+            [($fx= i j) str]
+            [else
+             (let ([b0 ($bytevector-u8-ref x i)])
+               (cond
+                 [($fx<= b0 #x7F) 
+                  ($string-set! str n ($fixnum->char b0))
+                  (f str x ($fxadd1 i) j ($fxadd1 n) mode)]
+                 [($fx= ($fxsra b0 5) #b110)
+                  (let ([i ($fxadd1 i)])
+                    (cond
+                      [($fx< i j) 
+                       (let ([b1 ($bytevector-u8-ref x i)])
+                         (cond
+                           [($fx= ($fxsra b1 6) #b10) 
+                            ($string-set! str n 
+                              ($fixnum->char 
+                                ($fx+ ($fxlogand b1 #b111111)
+                                      ($fxsll ($fxlogand b0 #b11111) 6))))
+                            (f str x ($fxadd1 i) j ($fxadd1 n) mode)]
+                           [(eq? mode 'ignore) 
+                            (f str x i j n mode)]
+                           [(eq? mode 'replace)
+                            ($string-set! str n ($fixnum->char #xFFFD))
+                            (f str x i j ($fxadd1 n) mode)]
+                           [else (error who "BUG")]))]
+                      [(eq? mode 'ignore) str]
+                      [(eq? mode 'replace) 
+                       ($string-set! str n ($fixnum->char #xFFFD))
+                       str]
+                      [else (error who "BUG")]))]
+                 [($fx= ($fxsra b0 4) #b1110)
+                  (cond
+                    [($fx< ($fx+ i 2) j) 
+                     (let ([b1 ($bytevector-u8-ref x ($fx+ i 1))]
+                           [b2 ($bytevector-u8-ref x ($fx+ i 2))])
+                       (cond
+                         [($fx= ($fxsra ($fxlogor b1 b2) 6) #b10)
+                          ($string-set! str n 
+                             ($fixnum->char 
+                               ($fx+ ($fxlogand b2 #b111111)
+                                 ($fx+ ($fxsll ($fxlogand b1 #b111111) 6)
+                                   ($fxsll ($fxlogand b0 #b1111) 12)))))
+                          (f str x ($fx+ i 3) j ($fxadd1 n) mode)]
+                         [(eq? mode 'ignore) 
+                          (f str x ($fxadd1 i) j n mode)]
+                         [(eq? mode 'replace)
+                          ($string-set! str n ($fixnum->char #xFFFD))
+                          (f str x ($fxadd1 i) j ($fxadd1 n) mode)]
+                         [else (error who "BUG")]))]
+                    [(eq? mode 'ignore) (f str x ($fxadd1 i) j n mode)]
+                    [(eq? mode 'replace) 
+                     ($string-set! str n ($fixnum->char #xFFFD))
+                     (f str x ($fxadd1 i) j ($fxadd1 n) mode)]
+                    [else (error who "BUG: incomplete char sequence")])]
+                 [($fx= ($fxsra b0 3) #b11110)
+                  (cond
+                    [($fx< ($fx+ i 3) j) 
+                     (let ([b1 ($bytevector-u8-ref x ($fx+ i 1))]
+                           [b2 ($bytevector-u8-ref x ($fx+ i 2))]
+                           [b3 ($bytevector-u8-ref x ($fx+ i 3))])
+                       (cond
+                         [($fx= ($fxsra ($fxlogor b1 ($fxlogor b2 b3)) 6) #b10)
+                          ($string-set! str n 
+                            ($fixnum->char 
+                              ($fx+ ($fxlogand b3 #b111111)
+                                ($fx+ ($fxsll ($fxlogand b2 #b111111) 6)
+                                  ($fx+ ($fxsll ($fxlogand b1 #b111111) 12)
+                                    ($fxsll ($fxlogand b0 #b111) 18))))))
+                          (f str x ($fx+ i 4) j ($fxadd1 n) mode)]
+                         [(eq? mode 'ignore)
+                          (f str x ($fxadd1 i) j n mode)]
+                         [(eq? mode 'replace)
+                          ($string-set! str n ($fixnum->char #xFFFD))
+                          (f str x ($fxadd1 i) j ($fxadd1 n) mode)]
+                         [else (error who "BUG")]))]
+                    [(eq? mode 'ignore) (f str x ($fxadd1 i) j n mode)]
+                    [(eq? mode 'replace) 
+                     ($string-set! str n ($fixnum->char #xFFFD))
+                     (f str x ($fxadd1 i) j ($fxadd1 n) mode)]
+                    [else (error who "BUG")])]
+                 [(eq? mode 'ignore) (f str x ($fxadd1 i) j n mode)]
+                 [(eq? mode 'replace)
+                  ($string-set! str n ($fixnum->char #xFFFD))
+                  (f str x ($fxadd1 i) j ($fxadd1 n) mode)]
+                 [else (error who "BUG")]))])))
+      (define (convert bv mode)
+        (fill ($make-string (count bv mode)) bv mode))
+      (case-lambda
+        [(bv) (convert bv 'error)]
+        [(bv handling-mode)
+         (unless (memq handling-mode '(ignore replace raise)) 
+           (error 'utf8-bytevector->string
+                  "~s is not a valid handling mode"
+                  handling-mode))
+         (convert bv handling-mode)])))
 
   )
 
 
 #!eof
-       (unless (memq handling-mode '(ignore replace raise)) 
-         (error 'string->utf8-bytevector "~s is not a valid hanlding-mode, shound be one of ignore, replace, or raise" handling-mode))
 
diff --git a/src/makefile.ss b/src/makefile.ss
index 69e4e72..421d776 100755
--- a/src/makefile.ss
+++ b/src/makefile.ss
@@ -39,6 +39,7 @@
     "ikarus.chars.ss"
     "ikarus.records.ss"
     "ikarus.strings.ss"
+    "ikarus.transcoders.ss"
     "ikarus.date-string.ss"
     "ikarus.symbols.ss"
     "ikarus.vectors.ss"
@@ -69,7 +70,6 @@
     "ikarus.posix.ss"
     "ikarus.timer.ss"
     "ikarus.bytevectors.ss"
-    "ikarus.transcoders.ss"
     "ikarus.main.ss"))
 
 (define ikarus-system-macros
@@ -293,6 +293,7 @@
     [uint-list->bytevector   i]
     [sint-list->bytevector   i]
     [string->utf8-bytevector i]
+    [utf8-bytevector->string i]
 
     [for-each                i r]
     [map                     i r]