diff --git a/app/api/announcements.py b/app/api/announcements.py
index 41d20eb..9cf851a 100644
--- a/app/api/announcements.py
+++ b/app/api/announcements.py
@@ -1,4 +1,4 @@
-from datetime import datetime
+from datetime import date, datetime
 
 from fastapi import APIRouter, Depends, HTTPException, Query
 from sqlalchemy import func, select
@@ -11,6 +11,12 @@ from app.models.schemas import AnnouncementListResponse, AnnouncementResponse
 router = APIRouter()
 
 
+def _parse_date(value: str | None) -> date | None:
+    if not value:
+        return None
+    return datetime.strptime(value, "%Y-%m-%d").date()
+
+
 @router.get("/announcements", response_model=AnnouncementListResponse)
 async def list_announcements(
     page: int = Query(1, ge=1),
@@ -27,10 +33,12 @@ async def list_announcements(
         conditions.append(Announcement.source_code == source_code)
     if crawl_mode:
         conditions.append(Announcement.crawl_mode == crawl_mode)
-    if start_date:
-        conditions.append(Announcement.publish_date >= start_date)
-    if end_date:
-        conditions.append(Announcement.publish_date <= end_date)
+    start = _parse_date(start_date)
+    end = _parse_date(end_date)
+    if start:
+        conditions.append(Announcement.publish_date >= start)
+    if end:
+        conditions.append(Announcement.publish_date <= end)
     if keyword:
         conditions.append(
             Announcement.title.ilike(f"%{keyword}%")