diff --git a/lilio/calendar.py b/lilio/calendar.py
index cf18e1f..7fb6c56 100644
--- a/lilio/calendar.py
+++ b/lilio/calendar.py
@@ -472,9 +472,15 @@ def _infer_time_bound(
         left = input_data.index.min()
         freq = xr.infer_freq(input_data.index)
         if freq is not None:
-            time_delta = pd.Timedelta(freq)
-            right += time_delta / 2
-            left -= time_delta / 2
+            try:
+                time_delta = pd.to_timedelta(freq)
+                right += time_delta / 2
+                left -= time_delta / 2
+            except ValueError as exc:
+                if "w/o a number" in str(exc) or "only leading negative" in str(exc):
+                    pass
+                else:
+                    raise exc
         return left, right
 
     def map_to_data(
diff --git a/tests/test_calendar.py b/tests/test_calendar.py
index ebcf448..b3f5251 100644
--- a/tests/test_calendar.py
+++ b/tests/test_calendar.py
@@ -385,7 +385,7 @@ def test_map_to_data_edge_case_first_year(self):
         # test the edge value when the input covers the anchor date
         cal = daily_calendar(anchor="10-15", length="180d")
         # multiple years covered
-        time_index = pd.date_range("20191010", "20211225", freq="60d")
+        time_index = pd.date_range("20190101", "20211225", freq="60d")
         test_data = np.random.random(len(time_index))
         timeseries = pd.Series(test_data, index=time_index)
         cal.map_to_data(timeseries)
@@ -408,7 +408,7 @@ def test_map_to_data_edge_case_first_year(self):
     def test_map_to_data_input_time_backward(self):
         # test when the input data has reverse order time index
         cal = daily_calendar(anchor="10-15", length="180d")
-        time_index = pd.date_range("20201010", "20211225", freq="60d")
+        time_index = pd.date_range("20200101", "20211225", freq="60d")
         test_data = np.random.random(len(time_index))
         timeseries = pd.Series(test_data, index=time_index[::-1])
         cal.map_to_data(timeseries)
@@ -427,7 +427,7 @@ def test_map_to_data_input_time_backward(self):
     def test_map_to_data_xarray_input(self):
         # test when the input data has reverse order time index
         cal = daily_calendar(anchor="10-15", length="180d")
-        time_index = pd.date_range("20201010", "20211225", freq="60d")
+        time_index = pd.date_range("20200101", "20211225", freq="60d")
         test_data = np.random.random(len(time_index))
         dataarray = xr.DataArray(data=test_data, coords={"time": time_index})
         cal.map_to_data(dataarray)