diff --git a/app/services/alpaca_price_service.py b/app/services/alpaca_price_service.py
index 07757a5..d5719e2 100644
--- a/app/services/alpaca_price_service.py
+++ b/app/services/alpaca_price_service.py
@@ -143,8 +143,8 @@ class AlpacaPriceService:
 
         # Phase 2: Alpaca HTTP (no DB session held)
         if need_fetch:
-            start_str = start_dt.strftime("%Y-%m-%d")
-            end_str = end_dt.strftime("%Y-%m-%d")
+            start_str = start_dt.strftime("%Y-%m-%dT%H:%M:%SZ")
+            end_str = end_dt.strftime("%Y-%m-%dT%H:%M:%SZ")
 
             # reverse-map: normalized Alpaca symbol → original input ticker
             reverse_map = {normalize_ticker(t): t for t in need_fetch}