diff --git a/wfdb/io/record.py b/wfdb/io/record.py
index 75ac1927..012a7b8a 100644
--- a/wfdb/io/record.py
+++ b/wfdb/io/record.py
@@ -1014,13 +1014,13 @@ def to_dataframe(self) -> pd.DataFrame:
             index = pd.date_range(
                 start=self.base_datetime,
                 periods=self.sig_len,
-                freq=pd.Timedelta(seconds=1 / self.fs),
+                end=self.get_absolute_time(self.sig_len - 1),
             )
         else:
             index = pd.timedelta_range(
                 start=pd.Timedelta(0),
                 periods=self.sig_len,
-                freq=pd.Timedelta(seconds=1 / self.fs),
+                end=self.get_elapsed_time(self.sig_len - 1),
             )
 
         if self.p_signal is not None: