fix(timeline): canonicalize browser timezone aliases

Author: AnkushMalaker

backends/advanced/src/advanced_omi_backend/routers/modules/timeline_routes.py

@@ -1,7 +1,6 @@
 """Authenticated semantic timeline APIs."""
 
 from datetime import date
-from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
 from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException, Query, Response
 from pydantic import BaseModel
@@ -17,16 +16,16 @@
     process_timeline_analysis_runs,
     request_timeline_analysis,
 )
+from advanced_omi_backend.services.timeline.timezone import canonical_timezone
 
 router = APIRouter(prefix="/timeline", tags=["timeline"])
 
 
 def _validate_timezone(value: str) -> str:
     try:
-        ZoneInfo(value)
-    except ZoneInfoNotFoundError as error:
+        return canonical_timezone(value)
+    except ValueError as error:
         raise HTTPException(status_code=422, detail="Unknown IANA timezone") from error
-    return value
 
 
 def _run_payload(run: TimelineAnalysisRun | None) -> dict | None:

backends/advanced/src/advanced_omi_backend/services/timeline/timezone.py

@@ -0,0 +1,31 @@
+"""Canonical IANA timezone handling for stable local-day identity."""
+
+from functools import lru_cache
+from pathlib import Path
+from zoneinfo import TZPATH, ZoneInfo, ZoneInfoNotFoundError
+
+
+@lru_cache(maxsize=1)
+def _timezone_aliases() -> dict[str, str]:
+    """Read the host tzdb link table so browser aliases share one day key."""
+
+    aliases: dict[str, str] = {}
+    for root in TZPATH:
+        link_table = Path(root) / "tzdata.zi"
+        if not link_table.is_file():
+            continue
+        for line in link_table.read_text(encoding="utf-8").splitlines():
+            if not line.startswith("L "):
+                continue
+            _, canonical, alias = line.split()
+            aliases[alias] = canonical
+        break
+    return aliases
+
+
+def canonical_timezone(value: str) -> str:
+    try:
+        ZoneInfo(value)
+    except ZoneInfoNotFoundError as error:
+        raise ValueError("unknown IANA timezone") from error
+    return _timezone_aliases().get(value, value)

backends/advanced/tests/test_timeline_timezone.py

@@ -0,0 +1,5 @@
+from advanced_omi_backend.services.timeline.timezone import canonical_timezone
+
+
+def test_legacy_browser_timezone_alias_is_canonicalized():
+    assert canonical_timezone("Asia/Calcutta") == "Asia/Kolkata"