diff --git a/judge/migrations/0118_convert_to_dates.py b/judge/migrations/0118_convert_to_dates.py
new file mode 100644
index 0000000000..94bdc3d92e
--- /dev/null
+++ b/judge/migrations/0118_convert_to_dates.py
@@ -0,0 +1,63 @@
+# Generated by Django 2.2.17 on 2021-04-27 14:46
+
+from django.db import migrations, models
+from django.db.models import F
+from django.utils import timezone
+
+
+def convert_to_datetime(apps, schema_editor):
+    Contest = apps.get_model('judge', 'Contest')
+    Submission = apps.get_model('judge', 'Submission')
+
+    Submission.objects.filter(was_rejudged=True).update(rejudged_date=F('judged_date'))
+    Submission.objects.filter(is_locked=True).update(locked_after=timezone.now())
+    Contest.objects.filter(is_locked=True).update(locked_after=F('end_time'))
+
+
+def convert_to_boolean(apps, schema_editor):
+    Contest = apps.get_model('judge', 'Contest')
+    Submission = apps.get_model('judge', 'Submission')
+
+    now = timezone.now()
+
+    Submission.objects.filter(rejudged_date__isnull=False).update(was_rejudged=True)
+    Submission.objects.filter(locked_after__lt=now).update(is_locked=True)
+    Contest.objects.filter(locked_after__lt=now).update(is_locked=True)
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('judge', '0117_remove_private_messages'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='contest',
+            name='locked_after',
+            field=models.DateTimeField(blank=True, help_text='Prevent submissions from this contest from being rejudged after this date.', null=True, verbose_name='contest lock'),
+        ),
+        migrations.AddField(
+            model_name='submission',
+            name='locked_after',
+            field=models.DateTimeField(blank=True, null=True, verbose_name='submission lock'),
+        ),
+        migrations.AddField(
+            model_name='submission',
+            name='rejudged_date',
+            field=models.DateTimeField(blank=True, null=True, verbose_name='last rejudge date by admin'),
+        ),
+        migrations.RunPython(convert_to_datetime, convert_to_boolean, atomic=True),
+        migrations.RemoveField(
+            model_name='contest',
+            name='is_locked',
+        ),
+        migrations.RemoveField(
+            model_name='submission',
+            name='is_locked',
+        ),
+        migrations.RemoveField(
+            model_name='submission',
+            name='was_rejudged',
+        ),
+    ]