diff --git a/apply.py b/apply.py
index 294b0cb..8cab090 100644
--- a/apply.py
+++ b/apply.py
@@ -5,8 +5,11 @@ from typing import Any
 logger = logging.getLogger(__name__)
 
 
-def _extract_uid(ical_data: bytes) -> str:
-    for line in ical_data.decode("utf-8", errors="replace").split("\r\n"):
+def _extract_uid(ical_data) -> str:
+    raw = ical_data
+    if isinstance(raw, bytes):
+        raw = raw.decode("utf-8", errors="replace")
+    for line in str(raw).split("\r\n"):
         if line.upper().startswith("UID:"):
             return line[4:].strip()
     return ""
@@ -15,7 +18,11 @@ def _extract_uid(ical_data: bytes) -> str:
 def _find_event_by_uid(calendar: Any, uid: str) -> Any | None:
     try:
         for event in calendar.events():
-            content = event.data.decode("utf-8", errors="replace")
+            raw = event.data
+            if isinstance(raw, bytes):
+                content = raw.decode("utf-8", errors="replace")
+            else:
+                content = str(raw)
             for line in content.split("\r\n"):
                 if line.upper().startswith("UID:"):
                     if line[4:].strip() == uid:
diff --git a/diff.py b/diff.py
index d0d4051..7f18706 100644
--- a/diff.py
+++ b/diff.py
@@ -5,6 +5,19 @@ from icalendar import Calendar
 logger = logging.getLogger(__name__)
 
 
+def _stable_event_key(component) -> str:
+    event_bytes = component.to_ical()
+    text = event_bytes.decode("utf-8", errors="replace")
+    stable_lines = []
+    for line in text.split("\r\n"):
+        key = line.split(":")[0].upper() if ":" in line else ""
+        if key in ("DTSTAMP", "LAST-MODIFIED"):
+            continue
+        stable_lines.append(line)
+    stable_text = "\r\n".join(stable_lines)
+    return hashlib.sha256(stable_text.encode("utf-8")).hexdigest()
+
+
 def parse_ics_events(ics_text: str) -> dict[str, str]:
     cal = Calendar.from_ical(ics_text.encode() if isinstance(ics_text, str) else ics_text)
     result = {}
@@ -17,9 +30,7 @@ def parse_ics_events(ics_text: str) -> dict[str, str]:
             continue
         uid_str = str(uid)
         try:
-            event_bytes = component.to_ical()
-            file_hash = hashlib.sha256(event_bytes).hexdigest()
-            result[uid_str] = file_hash
+            result[uid_str] = _stable_event_key(component)
         except Exception as e:
             logger.warning("Failed to process event %s: %s", uid_str, e)
     return result
diff --git a/sync_calendar.py b/sync_calendar.py
index b8c6e94..b265ab0 100644
--- a/sync_calendar.py
+++ b/sync_calendar.py
@@ -56,9 +56,14 @@ def sync_once(state: SyncState, health: HealthServer, config: Config) -> bool:
     logger.info("Starting sync cycle...")
 
     try:
-        r = requests.head(config.ics_url, headers=HEADERS, timeout=30, allow_redirects=True)
-        r.raise_for_status()
-        remote_etag = r.headers.get("ETag")
+        remote_etag = None
+        try:
+            r = requests.head(config.ics_url, headers=HEADERS, timeout=15, allow_redirects=True)
+            if r.status_code < 400:
+                remote_etag = r.headers.get("ETag")
+        except Exception:
+            pass
+
         cached_hash, cached_etag, _ = state.get_ics_cache()
 
         if remote_etag and cached_etag == remote_etag:
@@ -91,6 +96,8 @@ def sync_once(state: SyncState, health: HealthServer, config: Config) -> bool:
         to_update = deltas["to_update"]
         to_delete = deltas["to_delete"]
 
+        is_first_run = not state.get_event_uids() and not cached_hash
+
         if not to_add and not to_update and not to_delete:
             logger.info("Calendar is already in sync.")
             duration = time.time() - start_time
@@ -100,6 +107,24 @@ def sync_once(state: SyncState, health: HealthServer, config: Config) -> bool:
                 True,
                 len(ics_uids),
             )
+            for uid, h in ics_uids.items():
+                state.upsert_event(uid, h)
+            return True
+
+        if is_first_run and not to_delete:
+            logger.info(
+                "First run detected: %d events in ICS. Registering state without re-adding to calendar.",
+                len(to_add),
+            )
+            for uid, h in ics_uids.items():
+                state.upsert_event(uid, h)
+            duration = time.time() - start_time
+            health.update_status(
+                datetime.now(timezone.utc),
+                duration,
+                True,
+                len(ics_uids),
+            )
             return True
 
         logger.info(