diff --git a/monitoring/prober/scd/test_constraint_simple.py b/monitoring/prober/scd/test_constraint_simple.py
index 82be373cdf..386c2818af 100644
--- a/monitoring/prober/scd/test_constraint_simple.py
+++ b/monitoring/prober/scd/test_constraint_simple.py
@@ -123,6 +123,19 @@ def test_create_constraint_missing_time_end(ids, scd_api, scd_session):
     assert resp.status_code == 400, resp.content
 
 
+@for_api_versions(scd.API_0_3_17)
+@default_scope(SCOPE_CM)
+@depends_on(test_ensure_clean_workspace)
+def test_create_constraint_time_start_after_time_end(ids, scd_api, scd_session):
+    req = _make_c1_request()
+    e = req["extents"][0]
+    t = e["time_end"]
+    e["time_end"] = e["time_start"]
+    e["time_start"] = t
+    resp = scd_session.put(f"/constraint_references/{ids(CONSTRAINT_TYPE)}", json=req)
+    assert resp.status_code == 400, resp.content
+
+
 @for_api_versions(scd.API_0_3_17)
 @depends_on(test_ensure_clean_workspace)
 def test_create_constraint(ids, scd_api, scd_session):
diff --git a/monitoring/prober/scd/test_operation_simple.py b/monitoring/prober/scd/test_operation_simple.py
index 8bf6da2eaa..2161a21630 100644
--- a/monitoring/prober/scd/test_operation_simple.py
+++ b/monitoring/prober/scd/test_operation_simple.py
@@ -128,6 +128,18 @@ def test_create_op_missing_time_end(ids, scd_api, scd_session):
     assert resp.status_code == 400, resp.content
 
 
+@default_scope(SCOPE_SC)
+@depends_on(test_ensure_clean_workspace)
+def test_create_op_time_start_after_time_end(ids, scd_api, scd_session):
+    req = _make_op1_request()
+    e = req["extents"][0]
+    time_end = e["time_end"]
+    e["time_end"] = e["time_start"]
+    e["time_start"] = time_end
+    resp = scd_session.put(f"/operational_intent_references/{ids(OP_TYPE)}", json=req)
+    assert resp.status_code == 400, resp.content
+
+
 @depends_on(test_ensure_clean_workspace)
 def test_create_op(ids, scd_api, scd_session, scd_session_cp, scd_session_cm):
     req = _make_op1_request()
diff --git a/monitoring/prober/scd/test_subscription_simple.py b/monitoring/prober/scd/test_subscription_simple.py
index 4acfcd5850..7740f7a103 100644
--- a/monitoring/prober/scd/test_subscription_simple.py
+++ b/monitoring/prober/scd/test_subscription_simple.py
@@ -95,6 +95,18 @@ def test_sub_does_not_exist_query(ids, scd_api, scd_session):
     ]
 
 
+@for_api_versions(scd.API_0_3_17)
+@default_scope(SCOPE_SC)
+def test_create_sub_time_start_after_time_end(ids, scd_api, scd_session):
+    req = _make_sub1_req(scd_api)
+    e = req["extents"]
+    time_end = e["time_end"]
+    e["time_end"] = e["time_start"]
+    e["time_start"] = time_end
+    resp = scd_session.put(f"/subscriptions/{ids(SUB_TYPE)}", json=req)
+    assert resp.status_code == 400, resp.content
+
+
 @for_api_versions(scd.API_0_3_17)
 @default_scope(SCOPE_SC)
 def test_create_sub(ids, scd_api, scd_session):