diff --git a/fcore/app-update.sml b/fcore/app-update.sml
index fc4d5e0..b531ac7 100644
--- a/fcore/app-update.sml
+++ b/fcore/app-update.sml
@@ -2,6 +2,6 @@ structure AppUpdate =
 struct
   open AppType
 
-  fun update (app, msg) =
-    case #mode app of NORMAL_MODE str => NormalMode.update (app, str, msg)
+  fun update (app, msg, time) =
+    case #mode app of NORMAL_MODE str => NormalMode.update (app, str, msg, time)
 end
diff --git a/fcore/app-with.sml b/fcore/app-with.sml
index 9c0ecee..64ccf42 100644
--- a/fcore/app-with.sml
+++ b/fcore/app-with.sml
@@ -3,11 +3,13 @@ struct
   open AppType
 
   fun bufferAndSize
-    (app: app_type, newBuffer, newWidth, newHeight, newSearchList, newMsgs) =
+    (app: app_type, newBuffer, newWidth, newHeight, newSearchList, newMsgs,
+    newBufferModifyTime) =
     let
       val
         { mode
         , buffer = _
+        , bufferModifyTime = _
         , windowWidth = _
         , windowHeight = _
         , searchList = _
@@ -19,6 +21,7 @@ struct
     in
       { mode = mode
       , buffer = newBuffer
+      , bufferModifyTime = newBufferModifyTime
       , windowWidth = newWidth
       , windowHeight = newHeight
       , searchList = newSearchList
@@ -37,11 +40,13 @@ struct
     , newStartLine
     , newSearchList
     , newMsgs
+    , newBufferModifyTime
     ) =
     let
       val
         { mode = _
         , buffer = _
+        , bufferModifyTime = _
         , cursorIdx = _
         , startLine = _
         , searchList = _
@@ -53,6 +58,7 @@ struct
     in
       { mode = newMode
       , buffer = newBuffer
+      , bufferModifyTime = newBufferModifyTime
       , cursorIdx = newCursorIdx
       , startLine = newStartLine
       , searchList = newSearchList
@@ -69,6 +75,7 @@ struct
         { mode = _
         , msgs = _
         , buffer
+        , bufferModifyTime
         , searchList
         , searchString
         , cursorIdx
@@ -80,6 +87,7 @@ struct
       { mode = newMode
       , msgs = newMsgs
       , buffer = buffer
+      , bufferModifyTime = bufferModifyTime
       , searchList = searchList
       , searchString = searchString
       , cursorIdx = cursorIdx
@@ -89,11 +97,12 @@ struct
       }
     end
 
-  fun searchList (app: app_type, newSearchList, newBuffer, newSearchString) =
+  fun searchList (app: app_type, newSearchList, newBuffer, newSearchString, newBufferModifyTime) =
     let
       val
         { searchList = _
         , buffer = _
+        , bufferModifyTime
         , searchString = _
         , msgs
         , mode
@@ -105,6 +114,7 @@ struct
     in
       { searchList = newSearchList
       , buffer = newBuffer
+      , bufferModifyTime = newBufferModifyTime
       , searchString = newSearchString
       , msgs = msgs
       , mode = mode
@@ -120,6 +130,7 @@ struct
       val
         { startLine
         , buffer
+        , bufferModifyTime
         , searchList
         , searchString
         , mode
@@ -131,6 +142,7 @@ struct
     in
       { startLine = startLine
       , buffer = buffer
+      , bufferModifyTime = bufferModifyTime
       , searchList = searchList
       , searchString = searchString
       , mode = mode
diff --git a/fcore/finish.sml b/fcore/finish.sml
index c54598d..52f1e88 100644
--- a/fcore/finish.sml
+++ b/fcore/finish.sml
@@ -9,7 +9,8 @@ struct
   fun clearMode app =
     AppWith.mode (app, NORMAL_MODE "", [])
 
-  fun buildTextAndClear (app: app_type, buffer, cursorIdx, searchList, msgs) =
+  fun buildTextAndClear (app: app_type, buffer, cursorIdx, searchList, msgs,
+    bufferModifyTime) =
     let
       val {windowWidth, windowHeight, startLine, searchString, ...} = app
 
@@ -37,15 +38,15 @@ struct
       val mode = NORMAL_MODE ""
     in
       AppWith.bufferAndCursorIdx
-        (app, buffer, cursorIdx, mode, startLine, searchList, msgs)
+        (app, buffer, cursorIdx, mode, startLine, searchList, msgs, bufferModifyTime)
     end
 
   fun withSearchList (app: app_type, searchList) =
     let
-      val {buffer, searchString, cursorIdx, ...} = app
-      val app = AppWith.searchList (app, searchList, buffer, searchString)
+      val {buffer, searchString, cursorIdx, bufferModifyTime, ...} = app
+      val app = AppWith.searchList (app, searchList, buffer, searchString, bufferModifyTime)
     in
-      buildTextAndClear (app, buffer, cursorIdx, searchList, [])
+      buildTextAndClear (app, buffer, cursorIdx, searchList, [], bufferModifyTime)
     end
 
   fun resizeText (app: app_type, newWidth, newHeight) =
@@ -58,6 +59,7 @@ struct
         , cursorIdx
         , searchList
         , searchString
+        , bufferModifyTime
         , ...
         } = app
 
@@ -76,7 +78,7 @@ struct
         )
     in
       AppWith.bufferAndSize
-        (app, newBuffer, newWidth, newHeight, searchList, drawMsg)
+        (app, newBuffer, newWidth, newHeight, searchList, drawMsg, bufferModifyTime)
     end
 
   (* Difference between this and buildTextAndClear is that 
@@ -85,7 +87,7 @@ struct
    * Since the cursor may move away a lot, it is best to recenter.
    * *)
   fun buildTextAndClearAfterChr
-    (app: app_type, buffer, cursorIdx, searchList, initialMsg) =
+    (app: app_type, buffer, cursorIdx, searchList, initialMsg, bufferModifyTime) =
     let
       val {windowWidth, windowHeight, startLine, searchString, ...} = app
 
@@ -114,7 +116,7 @@ struct
       val mode = NORMAL_MODE ""
     in
       AppWith.bufferAndCursorIdx
-        (app, buffer, cursorIdx, mode, startLine, searchList, drawMsg)
+        (app, buffer, cursorIdx, mode, startLine, searchList, drawMsg, bufferModifyTime)
     end
 
   fun centreToCursor (app: app_type) =
@@ -127,6 +129,7 @@ struct
         , cursorIdx
         , searchList
         , searchString
+        , bufferModifyTime
         , ...
         } = app
       val buffer = LineGap.goToIdx (cursorIdx, buffer)
@@ -149,6 +152,6 @@ struct
         )
     in
       AppWith.bufferAndCursorIdx
-        (app, buffer, cursorIdx, NORMAL_MODE "", startLine, searchList, drawMsg)
+        (app, buffer, cursorIdx, NORMAL_MODE "", startLine, searchList, drawMsg, bufferModifyTime)
     end
 end
diff --git a/fcore/move.sml b/fcore/move.sml
index adc83d1..50d9043 100644
--- a/fcore/move.sml
+++ b/fcore/move.sml
@@ -12,7 +12,12 @@ functor MakeMove(Fn: MOVE): MAKE_MOVE =
 struct
   fun helpMove (app: AppType.app_type, buffer, cursorIdx, count) =
     if count = 0 then
-      Finish.buildTextAndClear (app, buffer, cursorIdx, #searchList app, [])
+      let
+        val {searchList, bufferModifyTime, ...} = app
+      in
+        Finish.buildTextAndClear (app, buffer, cursorIdx, searchList, [],
+        bufferModifyTime)
+      end
     else
       (* move LineGap to cursorIdx, which is necessary for finding newCursorIdx *)
       let
@@ -58,11 +63,11 @@ functor MakeDfaMove(Fn: DFA_MOVE): MAKE_DFA_MOVE =
 struct
   fun move (app: AppType.app_type, count) =
     let
-      val {buffer, cursorIdx, ...} = app
+      val {buffer, cursorIdx, searchList, bufferModifyTime, ...} = app
       val buffer = LineGap.goToIdx (cursorIdx, buffer)
       val cursorIdx = Fn.fMove (buffer, cursorIdx, count)
     in
-      Finish.buildTextAndClear (app, buffer, cursorIdx, #searchList app, [])
+      Finish.buildTextAndClear (app, buffer, cursorIdx, searchList, [], bufferModifyTime)
     end
 end
 
diff --git a/fcore/normal-mode/normal-move.sml b/fcore/normal-mode/normal-move.sml
index e1488b2..f8beb75 100644
--- a/fcore/normal-mode/normal-move.sml
+++ b/fcore/normal-mode/normal-move.sml
@@ -4,7 +4,8 @@ struct
 
   fun moveToStart (app: app_type) =
     let
-      val {buffer, windowWidth, windowHeight, searchList, searchString, ...} =
+      val {buffer, windowWidth, windowHeight, searchList, searchString,
+      bufferModifyTime, ...} =
         app
 
       val cursorIdx = 0
@@ -25,12 +26,13 @@ struct
       val mode = NORMAL_MODE ""
     in
       AppWith.bufferAndCursorIdx
-        (app, buffer, cursorIdx, mode, startLine, searchList, drawMsg)
+        (app, buffer, cursorIdx, mode, startLine, searchList, drawMsg, bufferModifyTime)
     end
 
   fun moveToEnd (app: app_type) =
     let
-      val {buffer, windowWidth, windowHeight, searchList, searchString, ...} =
+      val {buffer, windowWidth, windowHeight, searchList, searchString,
+      bufferModifyTime, ...} =
         app
 
       val buffer = LineGap.goToEnd buffer
@@ -66,7 +68,7 @@ struct
       val mode = NORMAL_MODE ""
     in
       AppWith.bufferAndCursorIdx
-        (app, buffer, bufferIdx, mode, bufferLine, searchList, drawMsg)
+        (app, buffer, bufferIdx, mode, bufferLine, searchList, drawMsg, bufferModifyTime)
     end
 
   fun moveToLine (app: app_type, reqLine) =
@@ -81,6 +83,7 @@ struct
           , startLine = origLine
           , searchList
           , searchString
+          , bufferModifyTime
           , ...
           } = app
         val buffer = LineGap.goToLine (reqLine, buffer)
@@ -109,7 +112,7 @@ struct
         val mode = NORMAL_MODE ""
       in
         AppWith.bufferAndCursorIdx
-          (app, buffer, cursorIdx, mode, startLine, searchList, drawMsg)
+          (app, buffer, cursorIdx, mode, startLine, searchList, drawMsg, bufferModifyTime)
       end
 
   fun moveToMatchingPair (app: app_type) =
@@ -122,6 +125,7 @@ struct
         , startLine
         , searchList
         , searchString
+        , bufferModifyTime
         , ...
         } = app
 
@@ -157,6 +161,7 @@ struct
             , startLine
             , searchList
             , drawMsg
+            , bufferModifyTime
             )
         end
       else
@@ -188,13 +193,15 @@ struct
             , startLine
             , searchList
             , drawMsg
+            , bufferModifyTime
             )
         end
     end
 
   fun firstNonSpaceChr (app: app_type) =
     let
-      val {buffer, cursorIdx, windowWidth, windowHeight, startLine, ...} = app
+      val {buffer, cursorIdx, windowWidth, windowHeight, startLine, searchList,
+      bufferModifyTime, ...} = app
 
       (* move LineGap and buffer to start of line *)
       val buffer = LineGap.goToIdx (cursorIdx, buffer)
@@ -204,13 +211,13 @@ struct
       val buffer = LineGap.goToIdx (cursorIdx, buffer)
       val cursorIdx = Cursor.firstNonSpaceChr (buffer, cursorIdx)
     in
-      Finish.buildTextAndClear (app, buffer, cursorIdx, #searchList app, [])
+      Finish.buildTextAndClear (app, buffer, cursorIdx, searchList, [], bufferModifyTime)
     end
 
   fun helpMoveToChr (app: app_type, buffer, cursorIdx, count, fMove, chr) =
     if count = 0 then
       Finish.buildTextAndClearAfterChr
-        (app, buffer, cursorIdx, #searchList app, [])
+        (app, buffer, cursorIdx, #searchList app, [], #bufferModifyTime app)
     else
       let
         (* move LineGap to cursorIdx, which is necessary for finding newCursorIdx *)
@@ -228,25 +235,25 @@ struct
 
   fun moveToNextMatch (app: app_type, count) =
     let
-      val {cursorIdx, searchList, buffer, ...} = app
+      val {cursorIdx, searchList, buffer, bufferModifyTime, ...} = app
       val newCursorIdx = SearchList.nextMatch (cursorIdx, searchList, count)
     in
       if newCursorIdx = ~1 then
         Finish.clearMode app
       else
         Finish.buildTextAndClearAfterChr
-          (app, buffer, newCursorIdx, searchList, [])
+          (app, buffer, newCursorIdx, searchList, [], bufferModifyTime)
     end
 
   fun moveToPrevMatch (app: app_type, count) =
     let
-      val {cursorIdx, searchList, buffer, ...} = app
+      val {cursorIdx, searchList, buffer, bufferModifyTime, ...} = app
       val newCursorIdx = SearchList.prevMatch (cursorIdx, searchList, count)
     in
       if newCursorIdx = ~1 then
         Finish.clearMode app
       else
         Finish.buildTextAndClearAfterChr
-          (app, buffer, newCursorIdx, searchList, [])
+          (app, buffer, newCursorIdx, searchList, [], bufferModifyTime)
     end
 end
diff --git a/shell/update-thread.sml b/shell/update-thread.sml
index 313f5d3..3a56833 100644
--- a/shell/update-thread.sml
+++ b/shell/update-thread.sml
@@ -20,20 +20,12 @@ struct
 
   fun loop (app: AppType.app_type, inputMailbox, drawMailbox, searchMailbox) =
     let
+      val time = Time.now ()
       val inputMsg = Mailbox.recv inputMailbox
-      val () =
-        (* if a certain CHAR_EVENT is sent, 
-         * we trigger an exception and log the command history.
-         * This is helpful for manually triggering logs when,
-         * for example, we encounter a bug and would like to see
-         * the history of events that caused it. *)
-        case inputMsg of
-          CHAR_EVENT #"~" => ExceptionLogger.log (Fail "")
-        | _ => ()
 
       val () = ExceptionLogger.addCommand inputMsg
 
-      val app = AppUpdate.update (app, inputMsg)
+      val app = AppUpdate.update (app, inputMsg, time)
                 handle e => ExceptionLogger.log e
 
       val () = sendMsgs (#msgs app, drawMailbox, searchMailbox)
diff --git a/shf-tests.mlb b/shf-tests.mlb
index 8285dd2..7786034 100644
--- a/shf-tests.mlb
+++ b/shf-tests.mlb
@@ -17,16 +17,6 @@ fcore/app-type.sml
 fcore/app-with.sml
 
 fcore/text-constants.sml
-ann
-  "allowVectorExps true"
-in
-  fcore/rect.sml
-  fcore/text-builder.sml
-  fcore/cursor-dfa/make-dfa-loop.sml
-  fcore/cursor-dfa/vi-WORD-dfa.sml
-  fcore/cursor-dfa/vi-word-dfa.sml
-  fcore/cursor-dfa/vi-dlr-dfa.sml
-end
 fcore/cursor.sml
 fcore/text-window.sml
 
@@ -34,18 +24,3 @@ fcore/finish.sml
 fcore/move.sml
 
 fcore/normal-mode/normal-move.sml
-fcore/normal-mode/normal-delete.sml
-fcore/normal-mode/normal-mode.sml
-
-fcore/app-update.sml
-
-(* TEST FILES *)
-$(SML_LIB)/basis/mlton.mlb
-
-shell/exception-logger.sml
-
-test/Railroad/src/railroad.mlb
-test/normal-move.sml
-test/normal-delete.sml
-test/regression.sml
-test/test.sml