Change Checkin.datetime to not auto_now_add

src/pretix/base/migrations/0052_auto_20161231_1533.py

@@ -0,0 +1,32 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.4 on 2016-12-31 15:33
+from __future__ import unicode_literals
+
+import django.db.models.deletion
+import django.utils.timezone
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0051_auto_20161221_1720'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='checkin',
+            name='datetime',
+            field=models.DateTimeField(default=django.utils.timezone.now),
+        ),
+        migrations.AlterField(
+            model_name='checkin',
+            name='position',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='checkins', to='pretixbase.OrderPosition'),
+        ),
+        migrations.AlterField(
+            model_name='voucher',
+            name='price_mode',
+            field=models.CharField(choices=[('none', 'No effect'), ('set', 'Set product price to'), ('subtract', 'Subtract from product price'), ('percent', 'Reduce product price by (%)')], default='none', max_length=100, verbose_name='Price mode'),
+        ),
+    ]

src/pretix/base/models/checkin.py

@@ -1,4 +1,5 @@
 from django.db import models
+from django.utils.timezone import now
 
 
 class Checkin(models.Model):
@@ -6,4 +7,4 @@ class Checkin(models.Model):
     A checkin object is created when a person enters the event.
     """
     position = models.ForeignKey('pretixbase.OrderPosition', related_name='checkins')
-    datetime = models.DateTimeField(auto_now_add=True)
+    datetime = models.DateTimeField(default=now)