diff --git a/html/admin.html b/html/admin.html
index 37d72f5..043ec44 100755
--- a/html/admin.html
+++ b/html/admin.html
@@ -588,29 +588,30 @@ window.onload = function() {
                     document.getElementById("sys_UTC_time").value = response.system_utc_time;
                     document.getElementById("RTC_utc_time").value = response.rtc_module_time;
 
-                    // Get the time difference
-                      const timeDiff = response.time_difference_seconds;
-
-                      // Reference to the alert container
+                    // Compare RTC time with browser time (more reliable than system time)
                       const alertContainer = document.getElementById("alert_container");
-
-                      // Remove any previous alert
                       alertContainer.innerHTML = "";
 
-                      // Add an alert based on time difference
-                    if (typeof timeDiff === "number") {
-                        if (timeDiff >= 0 && timeDiff <= 10) {
+                      if (response.rtc_module_time) {
+                        const rtcDate = new Date(response.rtc_module_time + ' UTC');
+                        const browserDate = new Date();
+                        const timeDiff = Math.abs(Math.round((browserDate - rtcDate) / 1000));
+
+                        if (timeDiff <= 30) {
                             alertContainer.innerHTML = `
                                 <div class="alert alert-success" role="alert">
-                                    RTC and system time are in sync (Difference: ${timeDiff} sec).
+                                    RTC synchronise avec l'heure du navigateur (ecart: ${timeDiff} sec).
                                 </div>`;
-                        } else if (timeDiff > 10) {
+                        } else {
+                            const minutes = Math.floor(timeDiff / 60);
+                            const label = minutes > 0 ? `${minutes} min ${timeDiff % 60} sec` : `${timeDiff} sec`;
                             alertContainer.innerHTML = `
                                 <div class="alert alert-danger" role="alert">
-                                    RTC time is out of sync! (Difference: ${timeDiff} sec).
+                                    RTC desynchronise ! Ecart avec le navigateur: ${label}.
+                                    Utilisez "Synchroniser le RTC" ci-dessous.
                                 </div>`;
                         }
-                    }
+                      }
               },
               error: function(xhr, status, error) {
                   console.error('AJAX request failed:', status, error);