diff --git a/python/ribasim/ribasim/delwaq/generate.py b/python/ribasim/ribasim/delwaq/generate.py
index e99abd63c..b4997915b 100644
--- a/python/ribasim/ribasim/delwaq/generate.py
+++ b/python/ribasim/ribasim/delwaq/generate.py
@@ -75,7 +75,7 @@ def _make_boundary(data, boundary_type):
         .reset_index(drop=True)
     )
     # Convert Arrow time to Numpy to avoid needing tzdata somehow
-    piv.time = pd.to_datetime(piv.time).dt.strftime("%Y-%m-%d %H:%M:%S")
+    piv.time = piv.time.astype("datetime64[ns]").dt.strftime("%Y-%m-%d %H:%M:%S")
     boundary = {
         "name": bid,
         "substances": list(map(_quote, piv.columns[1:])),
diff --git a/python/ribasim_testmodels/ribasim_testmodels/basic.py b/python/ribasim_testmodels/ribasim_testmodels/basic.py
index db0555c36..f431150a7 100644
--- a/python/ribasim_testmodels/ribasim_testmodels/basic.py
+++ b/python/ribasim_testmodels/ribasim_testmodels/basic.py
@@ -291,12 +291,12 @@ def tabulated_rating_curve_model() -> ribasim.Model:
             tabulated_rating_curve.Time(
                 time=[
                     # test millisecond precision
-                    pd.Timestamp("2020-01-01 00:00:00.001"),
-                    pd.Timestamp("2020-01-01 00:00:00.001"),
-                    pd.Timestamp("2020-02"),
-                    pd.Timestamp("2020-02"),
-                    pd.Timestamp("2020-03"),
-                    pd.Timestamp("2020-03"),
+                    pd.Timestamp("2020-01-01"),
+                    pd.Timestamp("2020-01-01"),
+                    pd.Timestamp("2020-02-01 00:00:00.001"),
+                    pd.Timestamp("2020-02-01 00:00:00.001"),
+                    pd.Timestamp("2020-03-01"),
+                    pd.Timestamp("2020-03-01"),
                 ],
                 level=[0.0, 1.0, 0.0, 1.1, 0.0, 1.2],
                 flow_rate=[0.0, 10 / 86400, 0.0, 10 / 86400, 0.0, 10 / 86400],