diff --git a/README.md b/README.md
index b4efeaa..756a322 100644
--- a/README.md
+++ b/README.md
@@ -34,7 +34,7 @@ _add_history() {
         local cmd=$(fc -ln -1)
         cmd=${cmd//$'\n'/\\n}
         shist add \
-            --timestamp "$(date --utc --iso-8601=seconds)" \
+            --timestamp "$(date -u +%Y-%m-%dT%H:%M:%S+00:00)" \
             --hostname "$(hostname)" \
             --dir "$(pwd)" \
             -- "$cmd"
@@ -46,10 +46,14 @@ hsup() { shist sync "$histdb_dir" }
 
 hs() {
     local copy_cmd=
-    case "$XDG_SESSION_TYPE" in
-        x11)     copy_cmd="xsel --clipboard" ;;
-        wayland) copy_cmd="wl-copy --trim-newline" ;;
-        *) echo "Session type not detected."; return ;;
+    case "$(uname -s)" in
+        Darwin) copy_cmd="pbcopy" ;;
+        *)
+            case "$XDG_SESSION_TYPE" in
+                x11)     copy_cmd="xsel --clipboard" ;;
+                wayland) copy_cmd="wl-copy --trim-newline" ;;
+                *) echo "Session type not detected."; return ;;
+            esac ;;
     esac
 
     local entry="$(