diff --git a/render_utils.py b/render_utils.py
index b099714..8a39d7e 100644
--- a/render_utils.py
+++ b/render_utils.py
@@ -116,6 +116,28 @@ def shift_clips(data, offset):
     return data
 
 
+def ass_timestamp(seconds):
+    hours = int(seconds // 3600)
+    minutes = int((seconds % 3600) // 60)
+    secs = seconds % 60
+
+    whole_seconds = int(secs)
+    centiseconds = int(round((secs - whole_seconds) * 100))
+
+    # Handle centisecond rollover (e.g., 59.999 → 60.00)
+    if centiseconds == 100:
+        whole_seconds += 1
+        centiseconds = 0
+        if whole_seconds == 60:
+            whole_seconds = 0
+            minutes += 1
+            if minutes == 60:
+                minutes = 0
+                hours += 1
+
+    return f"{hours}:{minutes:02d}:{whole_seconds:02d}.{centiseconds:02d}"
+
+
 def ass_encode(subs, options):
     if "lang" in options:
         langs = options["lang"].split(",")
@@ -158,8 +180,8 @@ Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour,
         "Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text"
     ]
     for sub in subs:
-        start = ox.format_timecode(sub["in"]).rstrip("0")
-        stop = ox.format_timecode(sub["out"]).rstrip("0")
+        start = ass_timestamp(sub["in"])
+        stop = ass_timestamp(sub["out"])
         for lang in reversed(langs):
             value = sub["values"][lang]
             event = f"Dialogue: 0,{start},{stop},{lang},,0,0,0,,{value}"