diff --git a/scripts/calibrate_ask.py b/scripts/calibrate_ask.py
index dba167a..05eee19 100644
--- a/scripts/calibrate_ask.py
+++ b/scripts/calibrate_ask.py
@@ -68,8 +68,10 @@ def parse_args() -> argparse.Namespace:
                    help="ask_events.source 필터 (eval / ui_search / ui_detail / 미지정=전체)")
     p.add_argument("--prompt-version", default=None,
                    help="ask_events.prompt_version 필터 (예: search_synthesis.v1-400char)")
-    p.add_argument("--since", default=None, help="ISO8601, created_at >= since")
-    p.add_argument("--until", default=None, help="ISO8601, created_at < until")
+    p.add_argument("--since", default=None, type=datetime.fromisoformat,
+                   help="ISO8601, created_at >= since")
+    p.add_argument("--until", default=None, type=datetime.fromisoformat,
+                   help="ISO8601, created_at < until")
     p.add_argument("--eval-split", choices=["tuning", "confirm", "all"], default="all",
                    help="source='eval' 일 때 holdout split")
     p.add_argument("--run-label", default=None, help="report 제목/파일명 라벨")