diff --git a/Un.cs b/Un.cs
index 0a7213d..5b42108 100644
--- a/Un.cs
+++ b/Un.cs
@@ -605,13 +605,31 @@ class Un
         catch (WebException ex)
         {
             string error = "";
+            int statusCode = 0;
             if (ex.Response != null)
             {
                 using (StreamReader reader = new StreamReader(ex.Response.GetResponseStream()))
                 {
                     error = reader.ReadToEnd();
                 }
+                if (ex.Response is HttpWebResponse httpResponse)
+                {
+                    statusCode = (int)httpResponse.StatusCode;
+                }
             }
+
+            // Check for clock drift errors
+            if (error.Contains("timestamp") && (statusCode == 401 || error.ToLower().Contains("expired") || error.ToLower().Contains("invalid")))
+            {
+                Console.Error.WriteLine($"{RED}Error: Request timestamp expired (must be within 5 minutes of server time){RESET}");
+                Console.Error.WriteLine($"{YELLOW}Your computer's clock may have drifted.{RESET}");
+                Console.Error.WriteLine("Check your system time and sync with NTP if needed:");
+                Console.Error.WriteLine("  Linux:   sudo ntpdate -s time.nist.gov");
+                Console.Error.WriteLine("  macOS:   sudo sntp -sS time.apple.com");
+                Console.Error.WriteLine("  Windows: w32tm /resync");
+                Environment.Exit(1);
+            }
+
             throw new Exception($"HTTP error - {error}");
         }
     }
diff --git a/Un.java b/Un.java
index bccf8eb..64a1dd2 100644
--- a/Un.java
+++ b/Un.java
@@ -555,6 +555,18 @@ public class Un {
         int status = conn.getResponseCode();
         if (status < 200 || status >= 300) {
             String error = readStream(conn.getErrorStream());
+
+            // Check for clock drift errors
+            if (error.contains("timestamp") && (status == 401 || error.toLowerCase().contains("expired") || error.toLowerCase().contains("invalid"))) {
+                System.err.println(RED + "Error: Request timestamp expired (must be within 5 minutes of server time)" + RESET);
+                System.err.println(YELLOW + "Your computer's clock may have drifted." + RESET);
+                System.err.println("Check your system time and sync with NTP if needed:");
+                System.err.println("  Linux:   sudo ntpdate -s time.nist.gov");
+                System.err.println("  macOS:   sudo sntp -sS time.apple.com");
+                System.err.println("  Windows: w32tm /resync");
+                System.exit(1);
+            }
+
             throw new Exception("HTTP " + status + " - " + error);
         }
 
diff --git a/un.clj b/un.clj
index 75787a9..406b680 100644
--- a/un.clj
+++ b/un.clj
@@ -127,6 +127,22 @@
   (let [message (str timestamp ":" method ":" path ":" body)]
     (hmac-sha256 secret-key message)))
 
+(defn check-clock-drift-error [response]
+  (let [has-timestamp (or (str/includes? response "timestamp")
+                          (str/includes? response "\"timestamp\""))
+        has-401 (str/includes? response "401")
+        has-expired (str/includes? response "expired")
+        has-invalid (str/includes? response "invalid")]
+    (when (and has-timestamp (or has-401 has-expired has-invalid))
+      (binding [*out* *err*]
+        (println (str red "Error: Request timestamp expired (must be within 5 minutes of server time)" reset))
+        (println (str yellow "Your computer's clock may have drifted." reset))
+        (println "Check your system time and sync with NTP if needed:")
+        (println "  Linux:   sudo ntpdate -s time.nist.gov")
+        (println "  macOS:   sudo sntp -sS time.apple.com")
+        (println "  Windows: w32tm /resync"))
+      (System/exit 1))))
+
 (defn build-auth-headers [public-key secret-key method path body]
   (if secret-key
     (let [timestamp (str (quot (System/currentTimeMillis) 1000))
@@ -148,6 +164,7 @@
                        ["-d" (str "@" tmp-file)])
           {:keys [out]} (apply sh args)]
       (io/delete-file tmp-file true)
+      (check-clock-drift-error out)
       out)))
 
 (defn curl-get [api-key endpoint]
@@ -155,16 +172,20 @@
         auth-headers (build-auth-headers public-key secret-key "GET" endpoint "")
         args (concat ["curl" "-s"
                       (str "https://api.unsandbox.com" endpoint)]
-                     auth-headers)]
-    (:out (apply sh args))))
+                     auth-headers)
+        result (:out (apply sh args))]
+    (check-clock-drift-error result)
+    result))
 
 (defn curl-delete [api-key endpoint]
   (let [[public-key secret-key] (get-api-keys)
         auth-headers (build-auth-headers public-key secret-key "DELETE" endpoint "")
         args (concat ["curl" "-s" "-X" "DELETE"
                       (str "https://api.unsandbox.com" endpoint)]
-                     auth-headers)]
-    (:out (apply sh args))))
+                     auth-headers)
+        result (:out (apply sh args))]
+    (check-clock-drift-error result)
+    result))
 
 (defn curl-portal-post [api-key endpoint json-data]
   (let [tmp-file (str "/tmp/un_clj_portal_" (rand-int 999999) ".json")
@@ -178,6 +199,7 @@
                        ["-d" (str "@" tmp-file)])
           {:keys [out]} (apply sh args)]
       (io/delete-file tmp-file true)
+      (check-clock-drift-error out)
       out)))
 
 (defn execute-command [file env-vars artifacts out-dir network vcpu]
diff --git a/un.cob b/un.cob
index 19ac291..0f32a47 100644
--- a/un.cob
+++ b/un.cob
@@ -293,14 +293,32 @@
                "openssl dgst -sha256 -hmac '"
                FUNCTION TRIM(WS-SECRET-KEY)
                "' | cut -d' ' -f2); "
-               "curl -s -X POST https://api.unsandbox.com/execute "
+               "RESP=$(curl -s -w '\n%{http_code}' -X POST "
+               "https://api.unsandbox.com/execute "
                "-H 'Content-Type: application/json' "
                "-H 'Authorization: Bearer "
                FUNCTION TRIM(WS-PUBLIC-KEY)
                "' "
                "-H 'X-Timestamp: '$TS "
                "-H 'X-Signature: '$SIG "
-               "--data-binary \"$BODY\" -o /tmp/unsandbox_resp.json; "
+               "--data-binary \"$BODY\"); "
+               "HTTP_CODE=$(echo \"$RESP\" | tail -n1); "
+               "BODY=$(echo \"$RESP\" | sed '$d'); "
+               "echo \"$BODY\" > /tmp/unsandbox_resp.json; "
+               "if echo \"$BODY\" | grep -q '\"timestamp\"' && "
+               "(echo \"$HTTP_CODE\" | grep -q '401' || "
+               "echo \"$BODY\" | grep -qi 'expired' || "
+               "echo \"$BODY\" | grep -qi 'invalid'); then "
+               "echo -e '\x1b[31mError: Request timestamp expired "
+               "(must be within 5 minutes of server time)\x1b[0m' >&2; "
+               "echo -e '\x1b[33mYour computer'"'"'s clock may have "
+               "drifted.\x1b[0m' >&2; "
+               "echo 'Check your system time and sync with NTP if "
+               "needed:' >&2; "
+               "echo '  Linux:   sudo ntpdate -s time.nist.gov' >&2; "
+               "echo '  macOS:   sudo sntp -sS time.apple.com' >&2; "
+               "echo '  Windows: w32tm /resync' >&2; "
+               "rm -f /tmp/unsandbox_resp.json; exit 1; fi; "
                "jq -r '.stdout // empty' /tmp/unsandbox_resp.json | "
                "sed 's/^/\x1b[34m/' | sed 's/$/\x1b[0m/'; "
                "jq -r '.stderr // empty' /tmp/unsandbox_resp.json | "
diff --git a/un.erl b/un.erl
index 816a5b4..f8b7c5d 100755
--- a/un.erl
+++ b/un.erl
@@ -322,6 +322,25 @@ make_signature(SecretKey, Timestamp, Method, Path, Body) ->
     Message = Timestamp ++ ":" ++ Method ++ ":" ++ Path ++ ":" ++ Body,
     hmac_sha256(SecretKey, Message).
 
+check_clock_drift_error(Response) ->
+    HasTimestamp = string:str(Response, "timestamp") > 0 orelse string:str(Response, "\"timestamp\"") > 0,
+    Has401 = string:str(Response, "401") > 0,
+    HasExpired = string:str(Response, "expired") > 0,
+    HasInvalid = string:str(Response, "invalid") > 0,
+
+    case HasTimestamp andalso (Has401 orelse HasExpired orelse HasInvalid) of
+        true ->
+            io:format(standard_error, "\033[31mError: Request timestamp expired (must be within 5 minutes of server time)\033[0m~n", []),
+            io:format(standard_error, "\033[33mYour computer's clock may have drifted.\033[0m~n", []),
+            io:format(standard_error, "Check your system time and sync with NTP if needed:~n", []),
+            io:format(standard_error, "  Linux:   sudo ntpdate -s time.nist.gov~n", []),
+            io:format(standard_error, "  macOS:   sudo sntp -sS time.apple.com~n", []),
+            io:format(standard_error, "  Windows: w32tm /resync~n", []),
+            halt(1);
+        false ->
+            ok
+    end.
+
 build_auth_headers(PublicKey, SecretKey, Method, Path, Body) ->
     if
         SecretKey =/= false ->
@@ -404,7 +423,9 @@ curl_post(ApiKey, Endpoint, TmpFile) ->
           " -H 'Content-Type: application/json'" ++
           AuthHeaders ++
           " -d @" ++ TmpFile,
-    os:cmd(Cmd).
+    Result = os:cmd(Cmd),
+    check_clock_drift_error(Result),
+    Result.
 
 curl_post_portal(ApiKey, Endpoint, Data) ->
     TmpFile = write_temp_file(Data),
@@ -416,6 +437,7 @@ curl_post_portal(ApiKey, Endpoint, Data) ->
           " -d @" ++ TmpFile,
     Result = os:cmd(Cmd),
     file:delete(TmpFile),
+    check_clock_drift_error(Result),
     Result.
 
 curl_get(ApiKey, Endpoint) ->
@@ -423,14 +445,18 @@ curl_get(ApiKey, Endpoint) ->
     AuthHeaders = build_auth_headers(PublicKey, SecretKey, "GET", Endpoint, ""),
     Cmd = "curl -s https://api.unsandbox.com" ++ Endpoint ++
           AuthHeaders,
-    os:cmd(Cmd).
+    Result = os:cmd(Cmd),
+    check_clock_drift_error(Result),
+    Result.
 
 curl_delete(ApiKey, Endpoint) ->
     {PublicKey, SecretKey} = get_api_keys(),
     AuthHeaders = build_auth_headers(PublicKey, SecretKey, "DELETE", Endpoint, ""),
     Cmd = "curl -s -X DELETE https://api.unsandbox.com" ++ Endpoint ++
           AuthHeaders,
-    os:cmd(Cmd).
+    Result = os:cmd(Cmd),
+    check_clock_drift_error(Result),
+    Result.
 
 %% Argument parsing
 parse_exec_args([], Opts) ->
diff --git a/un.ex b/un.ex
index eba8f7c..747c2ca 100755
--- a/un.ex
+++ b/un.ex
@@ -463,6 +463,7 @@ defmodule Un do
     {output, _exit} = System.cmd("curl", args, stderr_to_stdout: true)
 
     File.rm(tmp_file)
+    check_clock_drift(output)
     output
   end
 
@@ -497,6 +498,7 @@ defmodule Un do
     {output, _exit} = System.cmd("curl", args, stderr_to_stdout: true)
 
     File.rm(tmp_file)
+    check_clock_drift(output)
     output
   end
 
@@ -511,6 +513,7 @@ defmodule Un do
 
     {output, _exit} = System.cmd("curl", args, stderr_to_stdout: true)
 
+    check_clock_drift(output)
     output
   end
 
@@ -525,6 +528,7 @@ defmodule Un do
 
     {output, _exit} = System.cmd("curl", args, stderr_to_stdout: true)
 
+    check_clock_drift(output)
     output
   end
 
@@ -554,6 +558,26 @@ defmodule Un do
   defp get_opt([_arg | rest], long, short, default) do
     get_opt(rest, long, short, default)
   end
+
+  defp check_clock_drift(response) do
+    response_lower = String.downcase(response)
+
+    # Check if response contains "timestamp" and error indicators
+    has_timestamp = String.contains?(response_lower, "timestamp")
+    has_error = String.contains?(response_lower, "401") or
+                String.contains?(response_lower, "expired") or
+                String.contains?(response_lower, "invalid")
+
+    if has_timestamp and has_error do
+      IO.puts(:stderr, "#{@red}Error: Request timestamp expired (must be within 5 minutes of server time)#{@reset}")
+      IO.puts(:stderr, "#{@yellow}Your computer's clock may have drifted.")
+      IO.puts(:stderr, "Check your system time and sync with NTP if needed:")
+      IO.puts(:stderr, "  Linux:   sudo ntpdate -s time.nist.gov")
+      IO.puts(:stderr, "  macOS:   sudo sntp -sS time.apple.com")
+      IO.puts(:stderr, "  Windows: w32tm /resync#{@reset}")
+      System.halt(1)
+    end
+  end
 end
 
 Un.main(System.argv())
diff --git a/un.f90 b/un.f90
index f649300..da8e43e 100644
--- a/un.f90
+++ b/un.f90
@@ -167,6 +167,16 @@ contains
             '-H "X-Timestamp: $TS" ', &
             '-H "X-Signature: $SIG" ', &
             '--data-binary "$BODY" -o /tmp/unsandbox_resp.json; ', &
+            'RESP=$(cat /tmp/unsandbox_resp.json); ', &
+            'if echo "$RESP" | grep -q "timestamp" && ', &
+            '(echo "$RESP" | grep -Eq "(401|expired|invalid)"); then ', &
+            'echo -e "\x1b[31mError: Request timestamp expired (must be within 5 minutes of server time)\x1b[0m" >&2; ', &
+            'echo -e "\x1b[33mYour computer'\''s clock may have drifted.\x1b[0m" >&2; ', &
+            'echo "Check your system time and sync with NTP if needed:" >&2; ', &
+            'echo "  Linux:   sudo ntpdate -s time.nist.gov" >&2; ', &
+            'echo "  macOS:   sudo sntp -sS time.apple.com" >&2; ', &
+            'echo -e "  Windows: w32tm /resync\x1b[0m" >&2; ', &
+            'rm -f /tmp/unsandbox_resp.json; exit 1; fi; ', &
             'jq -r ".stdout // empty" /tmp/unsandbox_resp.json | ', &
             'sed "s/^/\x1b[34m/" | sed "s/$/\x1b[0m/"; ', &
             'jq -r ".stderr // empty" /tmp/unsandbox_resp.json | ', &
diff --git a/un.forth b/un.forth
index 9f73713..2698f3b 100644
--- a/un.forth
+++ b/un.forth
@@ -157,7 +157,21 @@
     s" TIMESTAMP=$(date +%s)" r@ write-line throw
     s" MESSAGE=\"$TIMESTAMP:POST:/execute:$BODY\"" r@ write-line throw
     s" SIGNATURE=$(echo -n \"$MESSAGE\" | openssl dgst -sha256 -hmac \"$SECRET_KEY\" -hex | sed 's/.*= //')" r@ write-line throw
-    s" curl -s -X POST https://api.unsandbox.com/execute -H 'Content-Type: application/json' -H \"Authorization: Bearer $PUBLIC_KEY\" -H \"X-Timestamp: $TIMESTAMP\" -H \"X-Signature: $SIGNATURE\" -d \"$BODY\" -o /tmp/unsandbox_resp.json; jq -r '.stdout // empty' /tmp/unsandbox_resp.json | sed 's/^/\\x1b[34m/' | sed 's/$/\\x1b[0m/'; jq -r '.stderr // empty' /tmp/unsandbox_resp.json | sed 's/^/\\x1b[31m/' | sed 's/$/\\x1b[0m/' >&2; rm -f /tmp/unsandbox_resp.json" r@ write-line throw
+    s" curl -s -X POST https://api.unsandbox.com/execute -H 'Content-Type: application/json' -H \"Authorization: Bearer $PUBLIC_KEY\" -H \"X-Timestamp: $TIMESTAMP\" -H \"X-Signature: $SIGNATURE\" -d \"$BODY\" -o /tmp/unsandbox_resp.json" r@ write-line throw
+    s" RESP=$(cat /tmp/unsandbox_resp.json)" r@ write-line throw
+    s" if echo \"$RESP\" | grep -q \"timestamp\" && (echo \"$RESP\" | grep -Eq \"(401|expired|invalid)\"); then" r@ write-line throw
+    s"   echo -e '\\x1b[31mError: Request timestamp expired (must be within 5 minutes of server time)\\x1b[0m' >&2" r@ write-line throw
+    s"   echo -e '\\x1b[33mYour computer'\\''s clock may have drifted.\\x1b[0m' >&2" r@ write-line throw
+    s"   echo 'Check your system time and sync with NTP if needed:' >&2" r@ write-line throw
+    s"   echo '  Linux:   sudo ntpdate -s time.nist.gov' >&2" r@ write-line throw
+    s"   echo '  macOS:   sudo sntp -sS time.apple.com' >&2" r@ write-line throw
+    s"   echo -e '  Windows: w32tm /resync\\x1b[0m' >&2" r@ write-line throw
+    s"   rm -f /tmp/unsandbox_resp.json" r@ write-line throw
+    s"   exit 1" r@ write-line throw
+    s" fi" r@ write-line throw
+    s" jq -r '.stdout // empty' /tmp/unsandbox_resp.json | sed 's/^/\\x1b[34m/' | sed 's/$/\\x1b[0m/'" r@ write-line throw
+    s" jq -r '.stderr // empty' /tmp/unsandbox_resp.json | sed 's/^/\\x1b[31m/' | sed 's/$/\\x1b[0m/' >&2" r@ write-line throw
+    s" rm -f /tmp/unsandbox_resp.json" r@ write-line throw
     r> close-file throw
 
     s" chmod +x /tmp/unsandbox_script.sh && /tmp/unsandbox_script.sh && rm -f /tmp/unsandbox_script.sh" system
diff --git a/un.fs b/un.fs
index b0d094b..c188647 100644
--- a/un.fs
+++ b/un.fs
@@ -279,6 +279,17 @@ let apiRequest (endpoint: string) (method: string) (data: (string * obj) list op
                 reader.ReadToEnd()
             else
                 ex.Message
+
+        // Check for clock drift error
+        if errorMsg.Contains("timestamp") && (errorMsg.Contains("401") || errorMsg.Contains("expired") || errorMsg.Contains("invalid")) then
+            eprintfn "%sError: Request timestamp expired (must be within 5 minutes of server time)%s" red reset
+            eprintfn "%sYour computer's clock may have drifted.%s" yellow reset
+            eprintfn "Check your system time and sync with NTP if needed:"
+            eprintfn "  Linux:   sudo ntpdate -s time.nist.gov"
+            eprintfn "  macOS:   sudo sntp -sS time.apple.com"
+            eprintfn "  Windows: w32tm /resync%s" reset
+            exit 1
+
         failwithf "HTTP error - %s" errorMsg
 
 let cmdExecute (args: Args) =
@@ -432,6 +443,17 @@ let cmdKey (args: Args) =
                 with _ -> body
             else
                 ex.Message
+
+        // Check for clock drift error
+        if errorMsg.Contains("timestamp") && (errorMsg.Contains("401") || errorMsg.Contains("expired") || errorMsg.Contains("invalid")) then
+            eprintfn "%sError: Request timestamp expired (must be within 5 minutes of server time)%s" red reset
+            eprintfn "%sYour computer's clock may have drifted.%s" yellow reset
+            eprintfn "Check your system time and sync with NTP if needed:"
+            eprintfn "  Linux:   sudo ntpdate -s time.nist.gov"
+            eprintfn "  macOS:   sudo sntp -sS time.apple.com"
+            eprintfn "  Windows: w32tm /resync%s" reset
+            exit 1
+
         printfn "Reason: %s" errorMsg
         exit 1
 
diff --git a/un.hs b/un.hs
index 3aa5127..dc15cf8 100644
--- a/un.hs
+++ b/un.hs
@@ -383,6 +383,28 @@ serviceCommand opts = do
           putStrLn $ green ++ "Service created" ++ reset
           putStrLn stdout
 
+-- Check for clock drift error
+checkClockDriftError :: String -> IO ()
+checkClockDriftError response = do
+  let hasTimestamp = "timestamp" `isPrefixOf` dropWhile (/= 't') response ||
+                     "\"timestamp\"" `isInfixOf` response
+  let has401 = "401" `isInfixOf` response
+  let hasExpired = "expired" `isInfixOf` response
+  let hasInvalid = "invalid" `isInfixOf` response
+
+  when (hasTimestamp && (has401 || hasExpired || hasInvalid)) $ do
+    hPutStrLn stderr $ red ++ "Error: Request timestamp expired (must be within 5 minutes of server time)" ++ reset
+    hPutStrLn stderr $ yellow ++ "Your computer's clock may have drifted." ++ reset
+    hPutStrLn stderr "Check your system time and sync with NTP if needed:"
+    hPutStrLn stderr "  Linux:   sudo ntpdate -s time.nist.gov"
+    hPutStrLn stderr "  macOS:   sudo sntp -sS time.apple.com"
+    hPutStrLn stderr "  Windows: w32tm /resync"
+    exitFailure
+  where
+    isInfixOf needle haystack = any (isPrefixOf needle) (tails haystack)
+    tails [] = [[]]
+    tails s@(_:xs) = s : tails xs
+
 -- HTTP helpers using curl
 curlPost :: String -> String -> String -> IO (ExitCode, String, String)
 curlPost apiKey url body = do
@@ -395,6 +417,8 @@ curlPost apiKey url body = do
      , url
      , "-H", "Content-Type: application/json"
      ] ++ authHeaders ++ ["-d", body]) ""
+  -- Check for clock drift error
+  checkClockDriftError stdout
   return (exitCode, stdout, stderr)
 
 curlGet :: String -> String -> IO (ExitCode, String, String)
@@ -402,16 +426,22 @@ curlGet apiKey url = do
   (publicKey, secretKey) <- getApiKeys
   let path = drop (length "https://api.unsandbox.com") url
   authHeaders <- buildAuthHeaders publicKey secretKey "GET" path ""
-  readProcessWithExitCode "curl"
+  (exitCode, stdout, stderr) <- readProcessWithExitCode "curl"
     ([ "-s", url ] ++ authHeaders) ""
+  -- Check for clock drift error
+  checkClockDriftError stdout
+  return (exitCode, stdout, stderr)
 
 curlDelete :: String -> String -> IO (ExitCode, String, String)
 curlDelete apiKey url = do
   (publicKey, secretKey) <- getApiKeys
   let path = drop (length "https://api.unsandbox.com") url
   authHeaders <- buildAuthHeaders publicKey secretKey "DELETE" path ""
-  readProcessWithExitCode "curl"
+  (exitCode, stdout, stderr) <- readProcessWithExitCode "curl"
     ([ "-s", "-X", "DELETE", url ] ++ authHeaders) ""
+  -- Check for clock drift error
+  checkClockDriftError stdout
+  return (exitCode, stdout, stderr)
 
 -- Get API keys from environment
 getApiKeys :: IO (String, Maybe String)
@@ -615,4 +645,6 @@ curlPostPortal apiKey url body = do
      , url
      , "-H", "Content-Type: application/json"
      ] ++ authHeaders ++ ["-d", body]) ""
+  -- Check for clock drift error
+  checkClockDriftError stdout
   return (exitCode, stdout, stderr)
diff --git a/un.lisp b/un.lisp
index c84a354..4eebbdb 100644
--- a/un.lisp
+++ b/un.lisp
@@ -101,40 +101,62 @@
             while line do (format out "~a~%" line))
       (uiop:wait-process process))))
 
+(defun check-clock-drift (response)
+  "Check if response indicates clock drift error"
+  (when (and (search "timestamp" response)
+             (or (search "401" response)
+                 (search "expired" response)
+                 (search "invalid" response)))
+    (format t "~aError: Request timestamp expired (must be within 5 minutes of server time)~a~%" *red* *reset*)
+    (format t "~aYour computer's clock may have drifted.~a~%" *yellow* *reset*)
+    (format t "Check your system time and sync with NTP if needed:~%")
+    (format t "  Linux:   sudo ntpdate -s time.nist.gov~%")
+    (format t "  macOS:   sudo sntp -sS time.apple.com~%")
+    (format t "  Windows: w32tm /resync~a~%" *reset*)
+    (uiop:quit 1)))
+
 (defun curl-post (api-key endpoint json-data)
   (let ((tmp-file (write-temp-file json-data)))
     (unwind-protect
          (destructuring-bind (public-key secret-key) (get-api-keys)
-           (let ((auth-headers (build-auth-headers public-key secret-key "POST" endpoint json-data))
-                 (base-args (list "curl" "-s" "-X" "POST"
-                                 (format nil "https://api.unsandbox.com~a" endpoint)
-                                 "-H" "Content-Type: application/json")))
-             (run-curl (append base-args auth-headers (list "-d" (format nil "@~a" tmp-file))))))
+           (let* ((auth-headers (build-auth-headers public-key secret-key "POST" endpoint json-data))
+                  (base-args (list "curl" "-s" "-X" "POST"
+                                  (format nil "https://api.unsandbox.com~a" endpoint)
+                                  "-H" "Content-Type: application/json"))
+                  (response (run-curl (append base-args auth-headers (list "-d" (format nil "@~a" tmp-file))))))
+             (check-clock-drift response)
+             response))
       (delete-file tmp-file))))
 
 (defun curl-get (api-key endpoint)
   (destructuring-bind (public-key secret-key) (get-api-keys)
-    (let ((auth-headers (build-auth-headers public-key secret-key "GET" endpoint ""))
-          (base-args (list "curl" "-s"
-                          (format nil "https://api.unsandbox.com~a" endpoint))))
-      (run-curl (append base-args auth-headers)))))
+    (let* ((auth-headers (build-auth-headers public-key secret-key "GET" endpoint ""))
+           (base-args (list "curl" "-s"
+                           (format nil "https://api.unsandbox.com~a" endpoint)))
+           (response (run-curl (append base-args auth-headers))))
+      (check-clock-drift response)
+      response)))
 
 (defun curl-delete (api-key endpoint)
   (destructuring-bind (public-key secret-key) (get-api-keys)
-    (let ((auth-headers (build-auth-headers public-key secret-key "DELETE" endpoint ""))
-          (base-args (list "curl" "-s" "-X" "DELETE"
-                          (format nil "https://api.unsandbox.com~a" endpoint))))
-      (run-curl (append base-args auth-headers)))))
+    (let* ((auth-headers (build-auth-headers public-key secret-key "DELETE" endpoint ""))
+           (base-args (list "curl" "-s" "-X" "DELETE"
+                           (format nil "https://api.unsandbox.com~a" endpoint)))
+           (response (run-curl (append base-args auth-headers))))
+      (check-clock-drift response)
+      response)))
 
 (defun curl-post-portal (api-key endpoint json-data)
   (let ((tmp-file (write-temp-file json-data)))
     (unwind-protect
          (destructuring-bind (public-key secret-key) (get-api-keys)
-           (let ((auth-headers (build-auth-headers public-key secret-key "POST" endpoint json-data))
-                 (base-args (list "curl" "-s" "-X" "POST"
-                                 (format nil "~a~a" *portal-base* endpoint)
-                                 "-H" "Content-Type: application/json")))
-             (run-curl (append base-args auth-headers (list "-d" (format nil "@~a" tmp-file))))))
+           (let* ((auth-headers (build-auth-headers public-key secret-key "POST" endpoint json-data))
+                  (base-args (list "curl" "-s" "-X" "POST"
+                                  (format nil "~a~a" *portal-base* endpoint)
+                                  "-H" "Content-Type: application/json"))
+                  (response (run-curl (append base-args auth-headers (list "-d" (format nil "@~a" tmp-file))))))
+             (check-clock-drift response)
+             response))
       (delete-file tmp-file))))
 
 (defun get-api-keys ()
diff --git a/un.m b/un.m
index d25b211..64edcc3 100644
--- a/un.m
+++ b/un.m
@@ -94,6 +94,24 @@ void getApiKeys(NSString** publicKey, NSString** secretKey) {
     }
 }
 
+void checkClockDrift(NSString* response) {
+    NSString* responseLower = [response lowercaseString];
+    if ([responseLower rangeOfString:@"timestamp"].location != NSNotFound &&
+        ([responseLower rangeOfString:@"401"].location != NSNotFound ||
+         [responseLower rangeOfString:@"expired"].location != NSNotFound ||
+         [responseLower rangeOfString:@"invalid"].location != NSNotFound)) {
+        fprintf(stderr, "%sError: Request timestamp expired (must be within 5 minutes of server time)%s\n",
+                [RED UTF8String], [RESET UTF8String]);
+        fprintf(stderr, "%sYour computer's clock may have drifted.%s\n",
+                [YELLOW UTF8String], [RESET UTF8String]);
+        fprintf(stderr, "Check your system time and sync with NTP if needed:\n");
+        fprintf(stderr, "  Linux:   sudo ntpdate -s time.nist.gov\n");
+        fprintf(stderr, "  macOS:   sudo sntp -sS time.apple.com\n");
+        fprintf(stderr, "  Windows: w32tm /resync%s\n", [RESET UTF8String]);
+        exit(1);
+    }
+}
+
 NSString* hmacSha256Hex(NSString* key, NSString* message) {
     const char* cKey = [key UTF8String];
     const char* cMessage = [message UTF8String];
@@ -170,6 +188,7 @@ NSDictionary* apiRequest(NSString* endpoint, NSString* method, NSDictionary* dat
         if (responseData) {
             NSString* errMsg = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
             fprintf(stderr, "%s\n", [errMsg UTF8String]);
+            checkClockDrift(errMsg);
         }
         exit(1);
     }
@@ -350,6 +369,7 @@ NSDictionary* portalRequest(NSString* endpoint, NSString* method, NSDictionary*
         if (responseData) {
             NSString* errMsg = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
             fprintf(stderr, "%s\n", [errMsg UTF8String]);
+            checkClockDrift(errMsg);
         }
         exit(1);
     }
diff --git a/un.ml b/un.ml
index dbd04e2..1fa77da 100755
--- a/un.ml
+++ b/un.ml
@@ -112,6 +112,31 @@ let escape_json s =
   ) s;
   Buffer.contents buf
 
+(* Check for clock drift errors *)
+let check_clock_drift response =
+  let response_lower = String.lowercase_ascii response in
+  let contains_substring s sub =
+    try
+      let _ = Str.search_forward (Str.regexp_string sub) s 0 in
+      true
+    with Not_found -> false
+  in
+  let has_timestamp = contains_substring response_lower "timestamp" in
+  let has_401 = contains_substring response_lower "401" in
+  let has_expired = contains_substring response_lower "expired" in
+  let has_invalid = contains_substring response_lower "invalid" in
+  let has_error = has_401 || has_expired || has_invalid in
+
+  if has_timestamp && has_error then begin
+    Printf.fprintf stderr "%sError: Request timestamp expired (must be within 5 minutes of server time)%s\n" red reset;
+    Printf.fprintf stderr "%sYour computer's clock may have drifted.\n" yellow;
+    Printf.fprintf stderr "Check your system time and sync with NTP if needed:\n";
+    Printf.fprintf stderr "  Linux:   sudo ntpdate -s time.nist.gov\n";
+    Printf.fprintf stderr "  macOS:   sudo sntp -sS time.apple.com\n";
+    Printf.fprintf stderr "  Windows: w32tm /resync%s\n" reset;
+    exit 1
+  end
+
 (* Execute curl command *)
 let curl_post api_key endpoint json =
   let (public_key, secret_key) = get_api_keys () in
@@ -130,6 +155,7 @@ let curl_post api_key endpoint json =
   let output = read_all "" in
   let _ = Unix.close_process_in ic in
   Sys.remove tmp_file;
+  check_clock_drift output;
   output
 
 let portal_curl_post api_key endpoint json =
@@ -149,6 +175,7 @@ let portal_curl_post api_key endpoint json =
   let output = read_all "" in
   let _ = Unix.close_process_in ic in
   Sys.remove tmp_file;
+  check_clock_drift output;
   output
 
 let curl_get api_key endpoint =
@@ -165,6 +192,7 @@ let curl_get api_key endpoint =
   in
   let output = read_all "" in
   let _ = Unix.close_process_in ic in
+  check_clock_drift output;
   output
 
 let curl_delete api_key endpoint =
@@ -181,6 +209,7 @@ let curl_delete api_key endpoint =
   in
   let output = read_all "" in
   let _ = Unix.close_process_in ic in
+  check_clock_drift output;
   output
 
 (* Extract JSON value - simple regex-based parser *)
diff --git a/un.pro b/un.pro
index efaf07c..9de79d2 100644
--- a/un.pro
+++ b/un.pro
@@ -128,7 +128,7 @@ execute_file(Filename) :-
 
     % Build and execute curl command with HMAC
     format(atom(Cmd),
-        'BODY=$(jq -Rs \'\'\''{language: "~w", code: .}\'\'\'\' < "~w"); TIMESTAMP=$(date +%s); MESSAGE="$TIMESTAMP:POST:/execute:$BODY"; SIGNATURE=$(echo -n "$MESSAGE" | openssl dgst -sha256 -hmac "~w" -hex | sed \'\'\'\'s/.*= //\'\'\'\'); curl -s -X POST https://api.unsandbox.com/execute -H "Content-Type: application/json" -H "Authorization: Bearer ~w" -H "X-Timestamp: $TIMESTAMP" -H "X-Signature: $SIGNATURE" -d "$BODY" -o /tmp/unsandbox_resp.json; jq -r ".stdout // empty" /tmp/unsandbox_resp.json | sed "s/^/\\x1b[34m/" | sed "s/$/\\x1b[0m/"; jq -r ".stderr // empty" /tmp/unsandbox_resp.json | sed "s/^/\\x1b[31m/" | sed "s/$/\\x1b[0m/" >&2; rm -f /tmp/unsandbox_resp.json',
+        'BODY=$(jq -Rs \'\'\''{language: "~w", code: .}\'\'\'\' < "~w"); TIMESTAMP=$(date +%s); MESSAGE="$TIMESTAMP:POST:/execute:$BODY"; SIGNATURE=$(echo -n "$MESSAGE" | openssl dgst -sha256 -hmac "~w" -hex | sed \'\'\'\'s/.*= //\'\'\'\'); curl -s -X POST https://api.unsandbox.com/execute -H "Content-Type: application/json" -H "Authorization: Bearer ~w" -H "X-Timestamp: $TIMESTAMP" -H "X-Signature: $SIGNATURE" -d "$BODY" -o /tmp/unsandbox_resp.json; RESP=$(cat /tmp/unsandbox_resp.json); if echo "$RESP" | grep -qi "timestamp" && echo "$RESP" | grep -Eqi "(401|expired|invalid)"; then echo -e "\\x1b[31mError: Request timestamp expired (must be within 5 minutes of server time)\\x1b[0m" >&2; echo -e "\\x1b[33mYour computer'\''s clock may have drifted.\\x1b[0m" >&2; echo "Check your system time and sync with NTP if needed:" >&2; echo "  Linux:   sudo ntpdate -s time.nist.gov" >&2; echo "  macOS:   sudo sntp -sS time.apple.com" >&2; echo "  Windows: w32tm /resync\\x1b[0m" >&2; rm -f /tmp/unsandbox_resp.json; exit 1; fi; jq -r ".stdout // empty" /tmp/unsandbox_resp.json | sed "s/^/\\x1b[34m/" | sed "s/$/\\x1b[0m/"; jq -r ".stderr // empty" /tmp/unsandbox_resp.json | sed "s/^/\\x1b[31m/" | sed "s/$/\\x1b[0m/" >&2; rm -f /tmp/unsandbox_resp.json',
         [Language, Filename, SecretKey, PublicKey]),
     shell(Cmd, 0).
 
@@ -137,7 +137,7 @@ session_list :-
     get_public_key(PublicKey),
     get_secret_key(SecretKey),
     format(atom(Cmd),
-        'TIMESTAMP=$(date +%s); MESSAGE="$TIMESTAMP:GET:/sessions:"; SIGNATURE=$(echo -n "$MESSAGE" | openssl dgst -sha256 -hmac "~w" -hex | sed \'\'s/.*= //\'\'); curl -s -X GET https://api.unsandbox.com/sessions -H "Authorization: Bearer ~w" -H "X-Timestamp: $TIMESTAMP" -H "X-Signature: $SIGNATURE" | jq -r \'.sessions[] | "\\(.id) \\(.shell) \\(.status) \\(.created_at)"\' 2>/dev/null || echo "No active sessions"',
+        'TIMESTAMP=$(date +%s); MESSAGE="$TIMESTAMP:GET:/sessions:"; SIGNATURE=$(echo -n "$MESSAGE" | openssl dgst -sha256 -hmac "~w" -hex | sed \'\'s/.*= //\'\'); RESP=$(curl -s -X GET https://api.unsandbox.com/sessions -H "Authorization: Bearer ~w" -H "X-Timestamp: $TIMESTAMP" -H "X-Signature: $SIGNATURE"); if echo "$RESP" | grep -qi "timestamp" && echo "$RESP" | grep -Eqi "(401|expired|invalid)"; then echo -e "\\x1b[31mError: Request timestamp expired (must be within 5 minutes of server time)\\x1b[0m" >&2; echo -e "\\x1b[33mYour computer'\''s clock may have drifted.\\x1b[0m" >&2; echo "Check your system time and sync with NTP if needed:" >&2; echo "  Linux:   sudo ntpdate -s time.nist.gov" >&2; echo "  macOS:   sudo sntp -sS time.apple.com" >&2; echo "  Windows: w32tm /resync\\x1b[0m" >&2; exit 1; fi; echo "$RESP" | jq -r \'.sessions[] | "\\(.id) \\(.shell) \\(.status) \\(.created_at)"\' 2>/dev/null || echo "No active sessions"',
         [SecretKey, PublicKey]),
     shell(Cmd, 0).
 
@@ -155,7 +155,7 @@ service_list :-
     get_public_key(PublicKey),
     get_secret_key(SecretKey),
     format(atom(Cmd),
-        'TIMESTAMP=$(date +%s); MESSAGE="$TIMESTAMP:GET:/services:"; SIGNATURE=$(echo -n "$MESSAGE" | openssl dgst -sha256 -hmac "~w" -hex | sed \'\'s/.*= //\'\'); curl -s -X GET https://api.unsandbox.com/services -H "Authorization: Bearer ~w" -H "X-Timestamp: $TIMESTAMP" -H "X-Signature: $SIGNATURE" | jq -r \'.services[] | "\\(.id) \\(.name) \\(.status)"\' 2>/dev/null || echo "No services"',
+        'TIMESTAMP=$(date +%s); MESSAGE="$TIMESTAMP:GET:/services:"; SIGNATURE=$(echo -n "$MESSAGE" | openssl dgst -sha256 -hmac "~w" -hex | sed \'\'s/.*= //\'\'); RESP=$(curl -s -X GET https://api.unsandbox.com/services -H "Authorization: Bearer ~w" -H "X-Timestamp: $TIMESTAMP" -H "X-Signature: $SIGNATURE"); if echo "$RESP" | grep -qi "timestamp" && echo "$RESP" | grep -Eqi "(401|expired|invalid)"; then echo -e "\\x1b[31mError: Request timestamp expired (must be within 5 minutes of server time)\\x1b[0m" >&2; echo -e "\\x1b[33mYour computer'\''s clock may have drifted.\\x1b[0m" >&2; echo "Check your system time and sync with NTP if needed:" >&2; echo "  Linux:   sudo ntpdate -s time.nist.gov" >&2; echo "  macOS:   sudo sntp -sS time.apple.com" >&2; echo "  Windows: w32tm /resync\\x1b[0m" >&2; exit 1; fi; echo "$RESP" | jq -r \'.services[] | "\\(.id) \\(.name) \\(.status)"\' 2>/dev/null || echo "No services"',
         [SecretKey, PublicKey]),
     shell(Cmd, 0).
 
@@ -252,11 +252,11 @@ validate_key(Extend) :-
     (   Extend = true
     ->  % Build command for --extend mode
         format(atom(Cmd),
-            'BODY=\'\'{}\'\'; TIMESTAMP=$(date +%s); MESSAGE="$TIMESTAMP:POST:/keys/validate:$BODY"; SIGNATURE=$(echo -n "$MESSAGE" | openssl dgst -sha256 -hmac "~w" -hex | sed \'\'s/.*= //\'\'); RESP=$(curl -s -X POST ~w/keys/validate -H "Content-Type: application/json" -H "Authorization: Bearer ~w" -H "X-Timestamp: $TIMESTAMP" -H "X-Signature: $SIGNATURE" -d "$BODY"); PUBLIC_KEY=$(echo "$RESP" | jq -r ".public_key // \\"N/A\\""); xdg-open "~w/keys/extend?pk=$PUBLIC_KEY" 2>/dev/null',
+            'BODY=\'\'{}\'\'; TIMESTAMP=$(date +%s); MESSAGE="$TIMESTAMP:POST:/keys/validate:$BODY"; SIGNATURE=$(echo -n "$MESSAGE" | openssl dgst -sha256 -hmac "~w" -hex | sed \'\'s/.*= //\'\'); RESP=$(curl -s -X POST ~w/keys/validate -H "Content-Type: application/json" -H "Authorization: Bearer ~w" -H "X-Timestamp: $TIMESTAMP" -H "X-Signature: $SIGNATURE" -d "$BODY"); if echo "$RESP" | grep -qi "timestamp" && echo "$RESP" | grep -Eqi "(401|expired|invalid)"; then echo -e "\\x1b[31mError: Request timestamp expired (must be within 5 minutes of server time)\\x1b[0m" >&2; echo -e "\\x1b[33mYour computer'\''s clock may have drifted.\\x1b[0m" >&2; echo "Check your system time and sync with NTP if needed:" >&2; echo "  Linux:   sudo ntpdate -s time.nist.gov" >&2; echo "  macOS:   sudo sntp -sS time.apple.com" >&2; echo "  Windows: w32tm /resync\\x1b[0m" >&2; exit 1; fi; PUBLIC_KEY=$(echo "$RESP" | jq -r ".public_key // \\"N/A\\""); xdg-open "~w/keys/extend?pk=$PUBLIC_KEY" 2>/dev/null',
             [SecretKey, PortalBase, PublicKey, PortalBase])
     ;   % Build command for normal validation
         format(atom(Cmd),
-            'BODY=\'\'{}\'\'; TIMESTAMP=$(date +%s); MESSAGE="$TIMESTAMP:POST:/keys/validate:$BODY"; SIGNATURE=$(echo -n "$MESSAGE" | openssl dgst -sha256 -hmac "~w" -hex | sed \'\'s/.*= //\'\'); curl -s -X POST ~w/keys/validate -H "Content-Type: application/json" -H "Authorization: Bearer ~w" -H "X-Timestamp: $TIMESTAMP" -H "X-Signature: $SIGNATURE" -d "$BODY" -o /tmp/unsandbox_key_resp.json; STATUS=$?; if [ $STATUS -ne 0 ]; then echo -e "\\x1b[31mInvalid\\x1b[0m"; exit 1; fi; EXPIRED=$(jq -r ".expired // false" /tmp/unsandbox_key_resp.json); if [ "$EXPIRED" = "true" ]; then echo -e "\\x1b[31mExpired\\x1b[0m"; echo "Public Key: $(jq -r ".public_key // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Tier: $(jq -r ".tier // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Expired: $(jq -r ".expires_at // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo -e "\\x1b[33mTo renew: Visit https://unsandbox.com/keys/extend\\x1b[0m"; rm -f /tmp/unsandbox_key_resp.json; exit 1; else echo -e "\\x1b[32mValid\\x1b[0m"; echo "Public Key: $(jq -r ".public_key // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Tier: $(jq -r ".tier // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Status: $(jq -r ".status // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Expires: $(jq -r ".expires_at // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Time Remaining: $(jq -r ".time_remaining // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Rate Limit: $(jq -r ".rate_limit // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Burst: $(jq -r ".burst // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Concurrency: $(jq -r ".concurrency // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; fi; rm -f /tmp/unsandbox_key_resp.json',
+            'BODY=\'\'{}\'\'; TIMESTAMP=$(date +%s); MESSAGE="$TIMESTAMP:POST:/keys/validate:$BODY"; SIGNATURE=$(echo -n "$MESSAGE" | openssl dgst -sha256 -hmac "~w" -hex | sed \'\'s/.*= //\'\'); curl -s -X POST ~w/keys/validate -H "Content-Type: application/json" -H "Authorization: Bearer ~w" -H "X-Timestamp: $TIMESTAMP" -H "X-Signature: $SIGNATURE" -d "$BODY" -o /tmp/unsandbox_key_resp.json; STATUS=$?; if [ $STATUS -ne 0 ]; then echo -e "\\x1b[31mInvalid\\x1b[0m"; exit 1; fi; RESP=$(cat /tmp/unsandbox_key_resp.json); if echo "$RESP" | grep -qi "timestamp" && echo "$RESP" | grep -Eqi "(401|expired|invalid)"; then echo -e "\\x1b[31mError: Request timestamp expired (must be within 5 minutes of server time)\\x1b[0m" >&2; echo -e "\\x1b[33mYour computer'\''s clock may have drifted.\\x1b[0m" >&2; echo "Check your system time and sync with NTP if needed:" >&2; echo "  Linux:   sudo ntpdate -s time.nist.gov" >&2; echo "  macOS:   sudo sntp -sS time.apple.com" >&2; echo "  Windows: w32tm /resync\\x1b[0m" >&2; rm -f /tmp/unsandbox_key_resp.json; exit 1; fi; EXPIRED=$(jq -r ".expired // false" /tmp/unsandbox_key_resp.json); if [ "$EXPIRED" = "true" ]; then echo -e "\\x1b[31mExpired\\x1b[0m"; echo "Public Key: $(jq -r ".public_key // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Tier: $(jq -r ".tier // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Expired: $(jq -r ".expires_at // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo -e "\\x1b[33mTo renew: Visit https://unsandbox.com/keys/extend\\x1b[0m"; rm -f /tmp/unsandbox_key_resp.json; exit 1; else echo -e "\\x1b[32mValid\\x1b[0m"; echo "Public Key: $(jq -r ".public_key // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Tier: $(jq -r ".tier // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Status: $(jq -r ".status // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Expires: $(jq -r ".expires_at // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Time Remaining: $(jq -r ".time_remaining // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Rate Limit: $(jq -r ".rate_limit // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Burst: $(jq -r ".burst // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; echo "Concurrency: $(jq -r ".concurrency // \\"N/A\\"" /tmp/unsandbox_key_resp.json)"; fi; rm -f /tmp/unsandbox_key_resp.json',
             [SecretKey, PortalBase, PublicKey])
     ),
     shell(Cmd, 0).
diff --git a/un.r b/un.r
index dd25ac8..e3a945f 100644
--- a/un.r
+++ b/un.r
@@ -93,6 +93,25 @@ get_api_keys <- function(args_key = NULL) {
     return(list(public_key = public_key, secret_key = secret_key))
 }
 
+check_clock_drift <- function(response_text) {
+    response_lower <- tolower(response_text)
+    has_timestamp <- grepl("timestamp", response_lower, fixed = TRUE)
+    has_401 <- grepl("401", response_lower, fixed = TRUE)
+    has_expired <- grepl("expired", response_lower, fixed = TRUE)
+    has_invalid <- grepl("invalid", response_lower, fixed = TRUE)
+    has_error <- has_401 || has_expired || has_invalid
+
+    if (has_timestamp && has_error) {
+        cat(sprintf("%sError: Request timestamp expired (must be within 5 minutes of server time)%s\n", RED, RESET), file = stderr())
+        cat(sprintf("%sYour computer's clock may have drifted.\n", YELLOW), file = stderr())
+        cat("Check your system time and sync with NTP if needed:\n", file = stderr())
+        cat("  Linux:   sudo ntpdate -s time.nist.gov\n", file = stderr())
+        cat("  macOS:   sudo sntp -sS time.apple.com\n", file = stderr())
+        cat(sprintf("  Windows: w32tm /resync%s\n", RESET), file = stderr())
+        quit(status = 1)
+    }
+}
+
 api_request <- function(endpoint, public_key, secret_key, method = "GET", data = NULL) {
     url <- paste0(API_BASE, endpoint)
     headers <- add_headers(
@@ -129,7 +148,9 @@ api_request <- function(endpoint, public_key, secret_key, method = "GET", data =
             stop(paste("Unsupported method:", method))
         }
 
-        result <- fromJSON(content(response, "text", encoding = "UTF-8"))
+        response_text <- content(response, "text", encoding = "UTF-8")
+        check_clock_drift(response_text)
+        result <- fromJSON(response_text)
         return(result)
     }, error = function(e) {
         cat(sprintf("%sError: Request failed: %s%s\n", RED, e$message, RESET), file = stderr())
@@ -292,7 +313,9 @@ cmd_key <- function(args) {
 
         tryCatch({
             response <- POST(url, headers, encode = "json", timeout(10))
-            result <- fromJSON(content(response, "text", encoding = "UTF-8"))
+            response_text <- content(response, "text", encoding = "UTF-8")
+            check_clock_drift(response_text)
+            result <- fromJSON(response_text)
 
             if (!is.null(result$public_key)) {
                 extend_url <- paste0(PORTAL_BASE, "/keys/extend?pk=", result$public_key)
@@ -331,7 +354,9 @@ cmd_key <- function(args) {
 
     tryCatch({
         response <- POST(url, headers, encode = "json", timeout(10))
-        result <- fromJSON(content(response, "text", encoding = "UTF-8"))
+        response_text <- content(response, "text", encoding = "UTF-8")
+        check_clock_drift(response_text)
+        result <- fromJSON(response_text)
 
         status <- if (!is.null(result$status)) result$status else "Unknown"
 
diff --git a/un.raku b/un.raku
index 1d93c9a..b50f80b 100644
--- a/un.raku
+++ b/un.raku
@@ -148,6 +148,17 @@ sub api-request(Str $endpoint, Str $method, %data?, Str :$public-key!, Str :$sec
         exit 1;
     }
 
+    # Check for clock drift errors
+    if $body.contains('timestamp') && ($body.contains('401') || $body.contains('expired') || $body.contains('invalid')) {
+        note "{$RED}Error: Request timestamp expired (must be within 5 minutes of server time){$RESET}";
+        note "{$YELLOW}Your computer's clock may have drifted.{$RESET}";
+        note "{$YELLOW}Check your system time and sync with NTP if needed:{$RESET}";
+        note "{$YELLOW}  Linux:   sudo ntpdate -s time.nist.gov{$RESET}";
+        note "{$YELLOW}  macOS:   sudo sntp -sS time.apple.com{$RESET}";
+        note "{$YELLOW}  Windows: w32tm /resync{$RESET}";
+        exit 1;
+    }
+
     return from-json($body);
 }
 
diff --git a/un.scm b/un.scm
index cf0f3f0..39ab8cd 100644
--- a/un.scm
+++ b/un.scm
@@ -117,6 +117,18 @@
                          (loop (cons line lines)))))))
     (close-pipe port)
     (delete-file tmp-file)
+    ;; Check for clock drift errors
+    (when (and (string-contains output "timestamp")
+               (or (string-contains output "401")
+                   (string-contains output "expired")
+                   (string-contains output "invalid")))
+      (format (current-error-port) "~aError: Request timestamp expired (must be within 5 minutes of server time)~a\n" red reset)
+      (format (current-error-port) "~aYour computer's clock may have drifted.~a\n" yellow reset)
+      (format (current-error-port) "~aCheck your system time and sync with NTP if needed:~a\n" yellow reset)
+      (format (current-error-port) "~a  Linux:   sudo ntpdate -s time.nist.gov~a\n" yellow reset)
+      (format (current-error-port) "~a  macOS:   sudo sntp -sS time.apple.com~a\n" yellow reset)
+      (format (current-error-port) "~a  Windows: w32tm /resync~a\n" yellow reset)
+      (exit 1))
     output))
 
 (define (curl-get api-key endpoint)
@@ -133,6 +145,18 @@
                          (string-join (reverse lines) "\n")
                          (loop (cons line lines)))))))
     (close-pipe port)
+    ;; Check for clock drift errors
+    (when (and (string-contains output "timestamp")
+               (or (string-contains output "401")
+                   (string-contains output "expired")
+                   (string-contains output "invalid")))
+      (format (current-error-port) "~aError: Request timestamp expired (must be within 5 minutes of server time)~a\n" red reset)
+      (format (current-error-port) "~aYour computer's clock may have drifted.~a\n" yellow reset)
+      (format (current-error-port) "~aCheck your system time and sync with NTP if needed:~a\n" yellow reset)
+      (format (current-error-port) "~a  Linux:   sudo ntpdate -s time.nist.gov~a\n" yellow reset)
+      (format (current-error-port) "~a  macOS:   sudo sntp -sS time.apple.com~a\n" yellow reset)
+      (format (current-error-port) "~a  Windows: w32tm /resync~a\n" yellow reset)
+      (exit 1))
     output))
 
 (define (curl-delete api-key endpoint)
@@ -149,6 +173,18 @@
                          (string-join (reverse lines) "\n")
                          (loop (cons line lines)))))))
     (close-pipe port)
+    ;; Check for clock drift errors
+    (when (and (string-contains output "timestamp")
+               (or (string-contains output "401")
+                   (string-contains output "expired")
+                   (string-contains output "invalid")))
+      (format (current-error-port) "~aError: Request timestamp expired (must be within 5 minutes of server time)~a\n" red reset)
+      (format (current-error-port) "~aYour computer's clock may have drifted.~a\n" yellow reset)
+      (format (current-error-port) "~aCheck your system time and sync with NTP if needed:~a\n" yellow reset)
+      (format (current-error-port) "~a  Linux:   sudo ntpdate -s time.nist.gov~a\n" yellow reset)
+      (format (current-error-port) "~a  macOS:   sudo sntp -sS time.apple.com~a\n" yellow reset)
+      (format (current-error-port) "~a  Windows: w32tm /resync~a\n" yellow reset)
+      (exit 1))
     output))
 
 (define (curl-post-portal api-key endpoint json-data)
@@ -169,6 +205,18 @@
                          (loop (cons line lines)))))))
     (close-pipe port)
     (delete-file tmp-file)
+    ;; Check for clock drift errors
+    (when (and (string-contains output "timestamp")
+               (or (string-contains output "401")
+                   (string-contains output "expired")
+                   (string-contains output "invalid")))
+      (format (current-error-port) "~aError: Request timestamp expired (must be within 5 minutes of server time)~a\n" red reset)
+      (format (current-error-port) "~aYour computer's clock may have drifted.~a\n" yellow reset)
+      (format (current-error-port) "~aCheck your system time and sync with NTP if needed:~a\n" yellow reset)
+      (format (current-error-port) "~a  Linux:   sudo ntpdate -s time.nist.gov~a\n" yellow reset)
+      (format (current-error-port) "~a  macOS:   sudo sntp -sS time.apple.com~a\n" yellow reset)
+      (format (current-error-port) "~a  Windows: w32tm /resync~a\n" yellow reset)
+      (exit 1))
     output))
 
 (define (get-api-keys)
diff --git a/un.zig b/un.zig
index 56eafa9..e336063 100644
--- a/un.zig
+++ b/un.zig
@@ -362,6 +362,21 @@ pub fn main() !u8 {
             defer allocator.free(json_content);
             std.fs.cwd().deleteFile(json_file) catch {};
 
+            // Check for clock drift errors
+            if (mem.indexOf(u8, json_content, "timestamp") != null and
+                (mem.indexOf(u8, json_content, "401") != null or
+                 mem.indexOf(u8, json_content, "expired") != null or
+                 mem.indexOf(u8, json_content, "invalid") != null))
+            {
+                std.debug.print("\x1b[31mError: Request timestamp expired (must be within 5 minutes of server time)\x1b[0m\n", .{});
+                std.debug.print("\x1b[33mYour computer's clock may have drifted.\x1b[0m\n", .{});
+                std.debug.print("\x1b[33mCheck your system time and sync with NTP if needed:\x1b[0m\n", .{});
+                std.debug.print("\x1b[33m  Linux:   sudo ntpdate -s time.nist.gov\x1b[0m\n", .{});
+                std.debug.print("\x1b[33m  macOS:   sudo sntp -sS time.apple.com\x1b[0m\n", .{});
+                std.debug.print("\x1b[33m  Windows: w32tm /resync\x1b[0m\n", .{});
+                return 1;
+            }
+
             // Simple JSON parsing to find public_key (looking for "public_key":"value")
             const pk_prefix = "\"public_key\":\"";
             var public_key_value: ?[]const u8 = null;
@@ -401,6 +416,21 @@ pub fn main() !u8 {
             defer allocator.free(json_content);
             std.fs.cwd().deleteFile(json_file) catch {};
 
+            // Check for clock drift errors
+            if (mem.indexOf(u8, json_content, "timestamp") != null and
+                (mem.indexOf(u8, json_content, "401") != null or
+                 mem.indexOf(u8, json_content, "expired") != null or
+                 mem.indexOf(u8, json_content, "invalid") != null))
+            {
+                std.debug.print("\x1b[31mError: Request timestamp expired (must be within 5 minutes of server time)\x1b[0m\n", .{});
+                std.debug.print("\x1b[33mYour computer's clock may have drifted.\x1b[0m\n", .{});
+                std.debug.print("\x1b[33mCheck your system time and sync with NTP if needed:\x1b[0m\n", .{});
+                std.debug.print("\x1b[33m  Linux:   sudo ntpdate -s time.nist.gov\x1b[0m\n", .{});
+                std.debug.print("\x1b[33m  macOS:   sudo sntp -sS time.apple.com\x1b[0m\n", .{});
+                std.debug.print("\x1b[33m  Windows: w32tm /resync\x1b[0m\n", .{});
+                return 1;
+            }
+
             // Simple JSON parsing (looking for specific fields)
             const status_prefix = "\"status\":\"";
             var status: ?[]const u8 = null;
@@ -535,14 +565,44 @@ pub fn main() !u8 {
     // Execute with curl
     const auth_headers = try buildAuthCmd(allocator, "POST", "/execute", json_content, public_key, secret_key);
     defer allocator.free(auth_headers);
-    const cmd = try std.fmt.allocPrint(allocator, "curl -s -X POST '{s}/execute' -H 'Content-Type: application/json' {s} -d @{s}", .{ API_BASE, auth_headers, json_file });
+    const response_file = "/tmp/unsandbox_response.json";
+    const cmd = try std.fmt.allocPrint(allocator, "curl -s -X POST '{s}/execute' -H 'Content-Type: application/json' {s} -d @{s} -o {s}", .{ API_BASE, auth_headers, json_file, response_file });
     defer allocator.free(cmd);
 
-    const result = std.c.system(cmd.ptr);
-    std.debug.print("\n", .{});
+    _ = std.c.system(cmd.ptr);
+
+    // Read response to check for clock drift errors
+    const response_content = fs.cwd().readFileAlloc(allocator, response_file, 10 * 1024 * 1024) catch |err| {
+        std.debug.print("\x1b[31mError reading response: {}\x1b[0m\n", .{err});
+        std.fs.cwd().deleteFile(json_file) catch {};
+        std.fs.cwd().deleteFile(response_file) catch {};
+        return 1;
+    };
+    defer allocator.free(response_content);
+
+    // Check for clock drift errors
+    if (mem.indexOf(u8, response_content, "timestamp") != null and
+        (mem.indexOf(u8, response_content, "401") != null or
+         mem.indexOf(u8, response_content, "expired") != null or
+         mem.indexOf(u8, response_content, "invalid") != null))
+    {
+        std.debug.print("\x1b[31mError: Request timestamp expired (must be within 5 minutes of server time)\x1b[0m\n", .{});
+        std.debug.print("\x1b[33mYour computer's clock may have drifted.\x1b[0m\n", .{});
+        std.debug.print("\x1b[33mCheck your system time and sync with NTP if needed:\x1b[0m\n", .{});
+        std.debug.print("\x1b[33m  Linux:   sudo ntpdate -s time.nist.gov\x1b[0m\n", .{});
+        std.debug.print("\x1b[33m  macOS:   sudo sntp -sS time.apple.com\x1b[0m\n", .{});
+        std.debug.print("\x1b[33m  Windows: w32tm /resync\x1b[0m\n", .{});
+        std.fs.cwd().deleteFile(json_file) catch {};
+        std.fs.cwd().deleteFile(response_file) catch {};
+        return 1;
+    }
+
+    // Print response
+    std.debug.print("{s}\n", .{response_content});
 
     // Cleanup
     std.fs.cwd().deleteFile(json_file) catch {};
+    std.fs.cwd().deleteFile(response_file) catch {};
 
-    return if (result == 0) 0 else 1;
+    return 0;
 }