Update main.py

main.py

@@ -3,7 +3,7 @@ from contextlib import contextmanager
 from datetime import date
 from flask import Flask, request, jsonify
 from flask_cors import CORS
-
+from datetime import date, datetime
 # ---- Optional Google GenAI (Gemini) ----
 from google import genai
 from google.genai import types
@@ -127,6 +127,19 @@ def embed_text_to_vec1536(text: str):
     )[0].tolist()
     return _pad(vec, VEC_DIM)
 
+def to_iso(d):
+    """Return YYYY-MM-DD for date/datetime/str; None for empty."""
+    if d is None:
+        return None
+    if isinstance(d, (date, datetime)):
+        return d.isoformat()[:10]
+    if isinstance(d, str):
+        return d[:10] if d else None
+    # fallback
+    try:
+        return str(d)[:10]
+    except Exception:
+        return None
 # ───────────────────────────────────────────────────────────────────────────────
 # GEMINI (explanations / descriptions)
 # ───────────────────────────────────────────────────────────────────────────────
@@ -202,7 +215,7 @@ def build_graph_from_events(obj_row, events):
         actor = ev.get("actor")
         place = ev.get("place")
         etype = ev.get("event_type") or "UNKNOWN"
-        d_iso = (ev.get("date_from") or "")[:10] if ev.get("date_from") else None
+        d_iso = to_iso(ev.get("date_from")) 
 
         actor_id = add_node("actor", actor) if actor else None
         place_id = add_node("place", place) if place else None
@@ -238,8 +251,8 @@ def build_timeline_from_events_and_sentences(events, sentences):
     items = []
     s_by_seq = {s["seq"]: s["sentence"] for s in sentences}
     for ev in events:
-        start = ev.get("date_from")
-        end   = ev.get("date_to")
+        start = to_iso(ev.get("date_from"))
+        end   = to_iso(ev.get("date_to"))
         title = ev.get("event_type") or "Event"
         txt   = None
         # Try to pull the nearest sentence by seq if present