diff --git a/src/sync_logic.rs b/src/sync_logic.rs
index aec434e..04bbadc 100644
--- a/src/sync_logic.rs
+++ b/src/sync_logic.rs
@@ -32,6 +32,7 @@ impl LtcFrame {
     /// Compare just HH:MM:SS against local time.
     pub fn matches_system_time(&self) -> bool {
         let local = Local::now();
+        // We only compare hours, minutes and seconds - frames are not considered in this comparison
         local.hour() == self.hours
             && local.minute() == self.minutes
             && local.second() == self.seconds
diff --git a/static/script.js b/static/script.js
index ba997a4..ccca735 100644
--- a/static/script.js
+++ b/static/script.js
@@ -101,22 +101,22 @@ document.addEventListener('DOMContentLoaded', () => {
                 let s = parseInt(tcParts[2], 10);
                 let f = parseInt(tcParts[3], 10);
 
+                const frameRateInt = Math.round(frameRate);
                 const msPerFrame = 1000.0 / frameRate;
                 const elapsedFrames = Math.floor(elapsedMs / msPerFrame);
 
-                f += elapsedFrames;
+                // Compute total seconds including fractional part
+                let totalSeconds = h * 3600 + m * 60 + s + f / frameRateInt;
+                totalSeconds += elapsedMs / 1000.0;
 
-                const frameRateInt = Math.round(frameRate);
-
-                s += Math.floor(f / frameRateInt);
-                f %= frameRateInt;
-
-                m += Math.floor(s / 60);
-                s %= 60;
-
-                h += Math.floor(m / 60);
-                m %= 60;
+                // Convert back to components
+                let newSeconds = Math.floor(totalSeconds);
+                f = Math.round((totalSeconds - newSeconds) * frameRateInt) % frameRateInt;
 
+                h = Math.floor(newSeconds / 3600);
+                newSeconds %= 3600;
+                m = Math.floor(newSeconds / 60);
+                s = Math.floor(newSeconds % 60);
                 h %= 24;
 
                 statusElements.ltcTimecode.textContent =