diff --git a/flexmeasures/utils/tests/test_time_utils.py b/flexmeasures/utils/tests/test_time_utils.py
index 196c7ae6c..961baf729 100644
--- a/flexmeasures/utils/tests/test_time_utils.py
+++ b/flexmeasures/utils/tests/test_time_utils.py
@@ -97,48 +97,72 @@ def test_naturalized_datetime_str(
 
 
 @pytest.mark.parametrize(
-    "window_size, now, exp_start, exp_end",
+    "window_size, now, exp_start, exp_end, grace_period",
     [
         (
             5,
             datetime(2021, 4, 30, 15, 1),
             datetime(2021, 4, 30, 14, 55),
             datetime(2021, 4, 30, 15),
+            0,
         ),
         (
             15,
             datetime(2021, 4, 30, 3, 36),
             datetime(2021, 4, 30, 3, 15),
             datetime(2021, 4, 30, 3, 30),
+            0,
+        ),
+        (
+            5,
+            datetime(2021, 4, 30, 9, 15, 16),
+            datetime(2021, 4, 30, 9, 10),
+            datetime(2021, 4, 30, 9, 15),
+            0,
         ),
         (
             10,
             datetime(2021, 4, 30, 0, 5),
             datetime(2021, 4, 29, 23, 50),
             datetime(2021, 4, 30, 0, 0),
+            0,
+        ),
+        (
+            5,
+            datetime(
+                2021, 5, 20, 10, 5, 34
+            ),  # less than grace period into the new window
+            datetime(2021, 5, 20, 9, 55),
+            datetime(2021, 5, 20, 10, 0),
+            60,
         ),
         (
             5,
-            datetime(2021, 5, 20, 10, 5, 34),  # boundary condition
+            datetime(2021, 5, 20, 10, 7, 4),
             datetime(2021, 5, 20, 9, 55),
             datetime(2021, 5, 20, 10, 0),
+            130,  # grace period > 2 minutes
         ),
         (
             60,
             datetime(2021, 1, 1, 0, 4),  # new year
             datetime(2020, 12, 31, 23, 00),
             datetime(2021, 1, 1, 0, 0),
+            0,
         ),
         (
             60,
             datetime(2021, 3, 28, 3, 10),  # DST transition
             datetime(2021, 3, 28, 2),
             datetime(2021, 3, 28, 3),
+            0,
         ),
     ],
 )
-def test_recent_clocktime_window(window_size, now, exp_start, exp_end):
-    start, end = get_most_recent_clocktime_window(window_size, now=now)
+def test_recent_clocktime_window(window_size, now, exp_start, exp_end, grace_period):
+    start, end = get_most_recent_clocktime_window(
+        window_size, now=now, grace_period_in_seconds=grace_period
+    )
     assert start == exp_start
     assert end == exp_end
 
diff --git a/flexmeasures/utils/time_utils.py b/flexmeasures/utils/time_utils.py
index 129e20998..ae3a69234 100644
--- a/flexmeasures/utils/time_utils.py
+++ b/flexmeasures/utils/time_utils.py
@@ -199,7 +199,9 @@ def get_most_recent_hour() -> datetime:
 
 
 def get_most_recent_clocktime_window(
-    window_size_in_minutes: int, now: Optional[datetime] = None
+    window_size_in_minutes: int,
+    now: Optional[datetime] = None,
+    grace_period_in_seconds: Optional[int] = 0,
 ) -> Tuple[datetime, datetime]:
     """
     Calculate a recent time window, returning a start and end minute so that
@@ -208,6 +210,9 @@ def get_most_recent_clocktime_window(
     Calling this function at 15:01:xx with window size 5 -> (14:55:00, 15:00:00)
     Calling this function at 03:36:xx with window size 15 -> (03:15:00, 03:30:00)
 
+    We can demand a grace period (of x seconds) to have passed before we are ready to accept that we're in a new window:
+    Calling this function at 15:00:16 with window size 5 and grace period of 30 seconds -> (14:50:00, 14:55:00)
+
     window_size_in_minutes is assumed to > 0 and < = 60, and a divisor of 60 (1, 2, ..., 30, 60).
 
     If now is not given, the current server time is used.
@@ -221,7 +226,13 @@ def get_most_recent_clocktime_window(
     assert 60 % window_size_in_minutes == 0
     if now is None:
         now = server_now()
-    last_full_minute = now.replace(second=0, microsecond=0) - timedelta(minutes=1)
+    last_full_minute = now.replace(second=0, microsecond=0)
+    if (
+        grace_period_in_seconds is not None
+        and grace_period_in_seconds > 0
+        and (now - last_full_minute).seconds < grace_period_in_seconds
+    ):
+        last_full_minute -= timedelta(minutes=1 + grace_period_in_seconds // 60)
     last_round_minute = last_full_minute.minute - (
         last_full_minute.minute % window_size_in_minutes
     )