diff --git a/src/sentry/models/groupopenperiod.py b/src/sentry/models/groupopenperiod.py
index dfadb3365b88d4..010a7df85988ce 100644
--- a/src/sentry/models/groupopenperiod.py
+++ b/src/sentry/models/groupopenperiod.py
@@ -98,8 +98,28 @@ def close_open_period(
             logger.warning("Open period is already closed", extra={"group_id": self.group.id})
             return
 
+        # We can't resolve issues before they started; if we've been asked to do so, the
+        # timestamp is likely from a different source than the date_started timestamp, and
+        # we should aim to fix that, so we warn.
+        # We ensure there's a valid close time so we can close the period as requested.
+        close_time = resolution_time
+        if resolution_time < self.date_started:
+            # There may be more externally accurate close times, but since we're closing it
+            # now, timezone.now() is arguably always a reasonable choice.
+            close_time = timezone.now()
+            logger.warning(
+                "Resolution time is before open period start time, using current time as close time",
+                extra={
+                    "group_id": self.group.id,
+                    "group_type": self.group.type,
+                    "resolution_time": resolution_time.isoformat(),
+                    "date_started": self.date_started.isoformat(),
+                    "close_time": close_time.isoformat(),
+                },
+            )
+
         self.update(
-            date_ended=resolution_time,
+            date_ended=close_time,
             resolution_activity=resolution_activity,
             user_id=resolution_activity.user_id,
         )
diff --git a/tests/sentry/models/test_groupopenperiod.py b/tests/sentry/models/test_groupopenperiod.py
new file mode 100644
index 00000000000000..a9cb64b29ceab3
--- /dev/null
+++ b/tests/sentry/models/test_groupopenperiod.py
@@ -0,0 +1,58 @@
+from datetime import timedelta
+
+from django.utils import timezone
+
+from sentry.incidents.grouptype import MetricIssue
+from sentry.models.activity import Activity
+from sentry.models.groupopenperiod import GroupOpenPeriod, create_open_period
+from sentry.testutils.cases import TestCase
+from sentry.types.activity import ActivityType
+
+
+class CloseOpenPeriodTest(TestCase):
+    def setUp(self) -> None:
+        super().setUp()
+        self.organization = self.create_organization()
+        self.project = self.create_project(organization=self.organization)
+        self.group = self.create_group(project=self.project, type=MetricIssue.type_id)
+
+        # Create an open period
+        self.start_time = timezone.now() - timedelta(hours=2)
+        create_open_period(self.group, self.start_time)
+        open_period = GroupOpenPeriod.objects.filter(group=self.group).first()
+        assert open_period is not None
+        assert open_period.date_ended is None
+        self.open_period = open_period
+
+    def test_close_open_period_resolution_time_before_start_time(self) -> None:
+        """
+        Test that when resolution_time is before date_started, we use current time
+        as the close time. This prevents DataError from PostgreSQL range constraint.
+        Since open periods track Sentry's internal view of when issues are open,
+        using current time is more accurate than creating a zero-duration period.
+        """
+        # Resolution time is 3 hours before the start time (problematic)
+        resolution_time = self.start_time - timedelta(hours=3)
+        activity = Activity.objects.create(
+            group=self.group,
+            project=self.project,
+            type=ActivityType.SET_RESOLVED.value,
+            user_id=self.user.id,
+        )
+
+        before_close = timezone.now()
+        self.open_period.close_open_period(
+            resolution_activity=activity,
+            resolution_time=resolution_time,
+        )
+        after_close = timezone.now()
+
+        # Should use current time as the close time, not the provided resolution_time
+        self.open_period.refresh_from_db()
+        assert self.open_period.date_ended is not None
+        assert self.open_period.date_ended != resolution_time
+        assert self.open_period.date_ended >= self.start_time
+        # Verify it's approximately now (within the test execution window)
+        assert before_close <= self.open_period.date_ended <= after_close
+        assert self.open_period.resolution_activity == activity
+        assert self.open_period.user_id == self.user.id