From ebbe2ee5d7d24b4087f6af58ddeb5958c0f34edc Mon Sep 17 00:00:00 2001
From: Akshay Kumar <akshaykumarhudedmani@gmail.com>
Date: Thu, 20 Aug 2026 22:49:08 +0530
Subject: [PATCH] fix(backtest): clamp right endpoint at calendar boundary to
 prevent IndexError

---
 qlib/backtest/utils.py | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/qlib/backtest/utils.py b/qlib/backtest/utils.py
index 4210c9548a8..ba5e69e4a1d 100644
--- a/qlib/backtest/utils.py
+++ b/qlib/backtest/utils.py
@@ -128,7 +128,16 @@ def get_step_time(self, trade_step: int | None = None, shift: int = 0) -> Tuple[
         if trade_step is None:
             trade_step = self.get_trade_step()
         calendar_index = self.start_index + trade_step - shift
-        return self._calendar[calendar_index], epsilon_change(self._calendar[calendar_index + 1])
+        if calendar_index + 1 < len(self._calendar):
+            right_time = self._calendar[calendar_index + 1]
+        else:
+            delta = (
+                self._calendar[calendar_index] - self._calendar[calendar_index - 1]
+                if calendar_index > 0
+                else pd.Timedelta(days=1)
+            )
+            right_time = self._calendar[calendar_index] + delta
+        return self._calendar[calendar_index], epsilon_change(right_time)
 
     def get_data_cal_range(self, rtype: str = "full") -> Tuple[int, int]:
         """