diff --git a/.gitignore b/.gitignore
index 1dd0855..c6c9f1a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -94,6 +94,9 @@ venv.bak/
 .spyderproject
 .spyproject
 
+# Visual Studio Code project settings
+.vscode
+
 # Rope project settings
 .ropeproject
 
diff --git a/epysurv/models/timeseries/_base.py b/epysurv/models/timeseries/_base.py
index a219b0a..4ad552e 100644
--- a/epysurv/models/timeseries/_base.py
+++ b/epysurv/models/timeseries/_base.py
@@ -21,4 +21,6 @@ def predict(self, data_generator) -> pd.DataFrame:
             [time] = prediction.index
             alarms.append(alarm)
             times.append(time)
-        return pd.DataFrame({"alarm": alarms}, index=pd.DatetimeIndex(times))
+        return pd.DataFrame(
+            {"alarm": alarms}, index=pd.DatetimeIndex(times, freq="infer")
+        )
diff --git a/tests/test_simulations.py b/tests/test_simulations.py
index 2ed5145..2a88c68 100644
--- a/tests/test_simulations.py
+++ b/tests/test_simulations.py
@@ -10,12 +10,7 @@
     SeasonalNoisePoisson,
 )
 
-
-def load_simulations(filepath):
-    simulations = pd.read_csv(
-        filepath, index_col=0, parse_dates=True, infer_datetime_format=True
-    )
-    return simulations
+from .utils import load_simulations
 
 
 @pytest.mark.parametrize(
diff --git a/tests/utils.py b/tests/utils.py
index 1d519c9..89bebf2 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -5,5 +5,13 @@ def load_predictions(filepath):
     predictions = pd.read_csv(
         filepath, index_col=0, parse_dates=True, infer_datetime_format=True
     ).assign(alarm=lambda df: df["alarm"].astype(bool))
+    freq = pd.infer_freq(predictions.index)
+    return predictions.asfreq(freq)
 
-    return predictions
+
+def load_simulations(filepath):
+    simulations = pd.read_csv(
+        filepath, index_col=0, parse_dates=True, infer_datetime_format=True
+    )
+    freq = pd.infer_freq(simulations.index)
+    return simulations.asfreq(freq)