diff --git a/biscuit/apps/chronos/forms.py b/biscuit/apps/chronos/forms.py
index 85d7b66f6681b013f6683af0860c01cba41fe1c9..f39cedc931a291c0b2113dcf3efc575a4e248f76 100644
--- a/biscuit/apps/chronos/forms.py
+++ b/biscuit/apps/chronos/forms.py
@@ -12,12 +12,15 @@ class SelectForm(forms.Form):
         queryset=Group.objects.annotate(lessons_count=Count('lessons')).filter(lessons_count__gt=0),
         label=_('Group'), required=False)
     teacher = forms.ModelChoiceField(
-        queryset=Person.objects.annotate(lessons_count=Count('lessons')).filter(lessons_count__gt=0),
+        queryset=Person.objects.annotate(lessons_count=Count(
+            'lessons')).filter(lessons_count__gt=0),
         label=_('Teacher'), required=False)
     room = forms.ModelChoiceField(
-        queryset=Room.objects.annotate(lessons_count=Count('lesson_periods')).filter(lessons_count__gt=0),
+        queryset=Room.objects.annotate(lessons_count=Count(
+            'lesson_periods')).filter(lessons_count__gt=0),
         label=_('Room'), required=False)
 
+
 class LessonSubstitutionForm(forms.ModelForm):
     class Meta:
         model = LessonSubstitution
diff --git a/biscuit/apps/chronos/migrations/0001_initial.py b/biscuit/apps/chronos/migrations/0001_initial.py
index b49d54adcb7469ee3cb01d85d573dca5a7286f6d..369b7bfc37d54e20e86a4f0ca74c75470fd46606 100644
--- a/biscuit/apps/chronos/migrations/0001_initial.py
+++ b/biscuit/apps/chronos/migrations/0001_initial.py
@@ -17,7 +17,8 @@ class Migration(migrations.Migration):
         migrations.CreateModel(
             name='Lesson',
             fields=[
-                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('id', models.AutoField(auto_created=True,
+                                        primary_key=True, serialize=False, verbose_name='ID')),
                 ('date_start', models.DateField(null=True, verbose_name='Effective start date of lesson')),
                 ('date_end', models.DateField(null=True, verbose_name='Effective end date of lesson')),
                 ('groups', models.ManyToManyField(related_name='lessons', to='core.Group')),
@@ -26,26 +27,34 @@ class Migration(migrations.Migration):
         migrations.CreateModel(
             name='Subject',
             fields=[
-                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
-                ('abbrev', models.CharField(max_length=10, verbose_name='Abbreviation of subject in timetable')),
+                ('id', models.AutoField(auto_created=True,
+                                        primary_key=True, serialize=False, verbose_name='ID')),
+                ('abbrev', models.CharField(max_length=10,
+                                            verbose_name='Abbreviation of subject in timetable')),
                 ('name', models.CharField(max_length=30, verbose_name='Long name of subject')),
-                ('colour_fg', models.CharField(blank=True, max_length=7, validators=[django.core.validators.RegexValidator('#[0-9A-F]{6}')], verbose_name='Foreground colour in timetable')),
-                ('colour_bg', models.CharField(blank=True, max_length=7, validators=[django.core.validators.RegexValidator('#[0-9A-F]{6}')], verbose_name='Background colour in timetable')),
+                ('colour_fg', models.CharField(blank=True, max_length=7, validators=[
+                 django.core.validators.RegexValidator('#[0-9A-F]{6}')], verbose_name='Foreground colour in timetable')),
+                ('colour_bg', models.CharField(blank=True, max_length=7, validators=[
+                 django.core.validators.RegexValidator('#[0-9A-F]{6}')], verbose_name='Background colour in timetable')),
             ],
         ),
         migrations.CreateModel(
             name='Room',
             fields=[
-                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
-                ('short_name', models.CharField(max_length=10, unique=True, verbose_name='Short name, e.g. room number')),
+                ('id', models.AutoField(auto_created=True,
+                                        primary_key=True, serialize=False, verbose_name='ID')),
+                ('short_name', models.CharField(max_length=10, unique=True,
+                                                verbose_name='Short name, e.g. room number')),
                 ('name', models.CharField(max_length=30, unique=True, verbose_name='Long name')),
             ],
         ),
         migrations.CreateModel(
             name='TimePeriod',
             fields=[
-                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
-                ('weekday', models.PositiveSmallIntegerField(choices=[(0, 'Sunday'), (1, 'Monday'), (2, 'Tuesday'), (3, 'Wednesday'), (4, 'Thursday'), (5, 'Friday'), (6, 'Saturday')], verbose_name='Week day')),
+                ('id', models.AutoField(auto_created=True,
+                                        primary_key=True, serialize=False, verbose_name='ID')),
+                ('weekday', models.PositiveSmallIntegerField(choices=[(0, 'Sunday'), (1, 'Monday'), (2, 'Tuesday'), (
+                    3, 'Wednesday'), (4, 'Thursday'), (5, 'Friday'), (6, 'Saturday')], verbose_name='Week day')),
                 ('period', models.PositiveSmallIntegerField(verbose_name='Number of period')),
                 ('time_start', models.TimeField(verbose_name='Time the period starts')),
                 ('time_end', models.TimeField(verbose_name='Time the period ends')),
@@ -54,21 +63,26 @@ class Migration(migrations.Migration):
         migrations.CreateModel(
             name='LessonPeriod',
             fields=[
-                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('id', models.AutoField(auto_created=True,
+                                        primary_key=True, serialize=False, verbose_name='ID')),
                 ('lesson', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='chronos.Lesson')),
-                ('period', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='chronos.TimePeriod')),
-                ('room', models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to='chronos.Room')),
+                ('period', models.ForeignKey(
+                    on_delete=django.db.models.deletion.CASCADE, to='chronos.TimePeriod')),
+                ('room', models.ForeignKey(null=True,
+                                           on_delete=django.db.models.deletion.CASCADE, to='chronos.Room')),
             ],
         ),
         migrations.AddField(
             model_name='lesson',
             name='periods',
-            field=models.ManyToManyField(related_name='lessons', through='chronos.LessonPeriod', to='chronos.TimePeriod'),
+            field=models.ManyToManyField(related_name='lessons',
+                                         through='chronos.LessonPeriod', to='chronos.TimePeriod'),
         ),
         migrations.AddField(
             model_name='lesson',
             name='subject',
-            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='lessons', to='chronos.Subject'),
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE,
+                                    related_name='lessons', to='chronos.Subject'),
         ),
         migrations.AddField(
             model_name='lesson',
diff --git a/biscuit/apps/chronos/migrations/0002_make_unique.py b/biscuit/apps/chronos/migrations/0002_make_unique.py
index 90f376fe4144eb0748e6d4074e74256c97d43ce7..d87921120c30fc25df400d4b98bc878f7c4a6710 100644
--- a/biscuit/apps/chronos/migrations/0002_make_unique.py
+++ b/biscuit/apps/chronos/migrations/0002_make_unique.py
@@ -13,7 +13,8 @@ class Migration(migrations.Migration):
         migrations.AlterField(
             model_name='subject',
             name='abbrev',
-            field=models.CharField(max_length=10, unique=True, verbose_name='Abbreviation of subject in timetable'),
+            field=models.CharField(max_length=10, unique=True,
+                                   verbose_name='Abbreviation of subject in timetable'),
         ),
         migrations.AlterField(
             model_name='subject',
@@ -32,6 +33,7 @@ class Migration(migrations.Migration):
         migrations.AlterField(
             model_name='room',
             name='short_name',
-            field=models.CharField(max_length=10, unique=True, verbose_name='Short name, e.g. room number'),
+            field=models.CharField(max_length=10, unique=True,
+                                   verbose_name='Short name, e.g. room number'),
         ),
     ]
diff --git a/biscuit/apps/chronos/migrations/0003_lesson_substitution.py b/biscuit/apps/chronos/migrations/0003_lesson_substitution.py
index d2bab865e852396e2ea1910ee640179781a113dc..b17774aaa6666452922a97e86368dbbdd6716fa7 100644
--- a/biscuit/apps/chronos/migrations/0003_lesson_substitution.py
+++ b/biscuit/apps/chronos/migrations/0003_lesson_substitution.py
@@ -15,15 +15,19 @@ class Migration(migrations.Migration):
         migrations.CreateModel(
             name='LessonSubstitution',
             fields=[
-                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
-                ('room', models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to='chronos.Room')),
-                ('subject', models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, related_name='lesson_substitutions', to='chronos.Subject')),
+                ('id', models.AutoField(auto_created=True,
+                                        primary_key=True, serialize=False, verbose_name='ID')),
+                ('room', models.ForeignKey(null=True,
+                                           on_delete=django.db.models.deletion.CASCADE, to='chronos.Room')),
+                ('subject', models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE,
+                                              related_name='lesson_substitutions', to='chronos.Subject')),
                 ('teachers', models.ManyToManyField(related_name='lesson_substitutions', to='core.Person')),
             ],
         ),
         migrations.AddField(
             model_name='lessonperiod',
             name='substitution',
-            field=models.OneToOneField(null=True, on_delete=django.db.models.deletion.CASCADE, related_name='lesson_period', to='chronos.LessonSubstitution'),
+            field=models.OneToOneField(null=True, on_delete=django.db.models.deletion.CASCADE,
+                                       related_name='lesson_period', to='chronos.LessonSubstitution'),
         ),
     ]
diff --git a/biscuit/apps/chronos/migrations/0004_auto_20190821_1550.py b/biscuit/apps/chronos/migrations/0004_auto_20190821_1550.py
index af74299244f2c098b8aaefe313e28848a2e1e515..303fbed299bbed7b13f391d99282b83c6fd90e15 100644
--- a/biscuit/apps/chronos/migrations/0004_auto_20190821_1550.py
+++ b/biscuit/apps/chronos/migrations/0004_auto_20190821_1550.py
@@ -19,12 +19,14 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='lessonsubstitution',
             name='lesson_period',
-            field=models.ForeignKey(default=1, on_delete=django.db.models.deletion.CASCADE, related_name='substitutions', to='chronos.LessonPeriod'),
+            field=models.ForeignKey(default=1, on_delete=django.db.models.deletion.CASCADE,
+                                    related_name='substitutions', to='chronos.LessonPeriod'),
             preserve_default=False,
         ),
         migrations.AddField(
             model_name='lessonsubstitution',
             name='week',
-            field=models.IntegerField(default=biscuit.apps.chronos.util.current_week, verbose_name='Kalenderwoche'),
+            field=models.IntegerField(
+                default=biscuit.apps.chronos.util.current_week, verbose_name='Kalenderwoche'),
         ),
     ]
diff --git a/biscuit/apps/chronos/models.py b/biscuit/apps/chronos/models.py
index dc24221519e21c4c697a022b1053236e2decfa80..0159ff7427f3340ba4d7386ab5e1928c9d94cef9 100644
--- a/biscuit/apps/chronos/models.py
+++ b/biscuit/apps/chronos/models.py
@@ -60,7 +60,7 @@ class Subject(models.Model):
         return '%s - %s' % (self.abbrev, self.name)
 
     class Meta:
-         ordering = ['name', 'abbrev']
+        ordering = ['name', 'abbrev']
 
 
 class Room(models.Model):
@@ -116,7 +116,8 @@ class LessonSubstitution(models.Model):
     room = models.ForeignKey('Room', models.CASCADE, null=True)
 
     class Meta:
-        ordering = ['lesson_period__lesson__date_start', 'week', 'lesson_period__period__weekday', 'lesson_period__period__period']
+        ordering = ['lesson_period__lesson__date_start', 'week',
+                    'lesson_period__period__weekday', 'lesson_period__period__period']
 
 
 class LessonPeriod(models.Model):
diff --git a/biscuit/apps/chronos/tables.py b/biscuit/apps/chronos/tables.py
index c1a55c4ef47d61e31299e5a43a6ddc206a7bdb26..12a0d4ac4a549f7bea013eba1dbaec1e459c5c6a 100644
--- a/biscuit/apps/chronos/tables.py
+++ b/biscuit/apps/chronos/tables.py
@@ -26,4 +26,5 @@ class LessonsTable(tables.Table):
     lesson__teachers = tables.Column(accessor='lesson.teacher_names', verbose_name=_('Teachers'))
     lesson__subject = tables.Column(accessor='lesson.subject')
     room = tables.Column(accessor='room')
-    edit_substitution = tables.LinkColumn('edit_substitution', args=[A('id'), A('_week')], text=_('Substitution'))
+    edit_substitution = tables.LinkColumn(
+        'edit_substitution', args=[A('id'), A('_week')], text=_('Substitution'))
diff --git a/biscuit/apps/chronos/views.py b/biscuit/apps/chronos/views.py
index 92f0ab18de2f98de45a5209a33582fe966101bde..01f355eada74e247893d9d8d33cf067ac41fcd06 100644
--- a/biscuit/apps/chronos/views.py
+++ b/biscuit/apps/chronos/views.py
@@ -102,7 +102,7 @@ def lessons_day(request: HttpRequest, when: Optional[str] = None) -> HttpRespons
     )
 
     # Build table
-    lessons_table = LessonsTable(lesson_periods.extra(select = {'_week': week}).all())
+    lessons_table = LessonsTable(lesson_periods.extra(select={'_week': week}).all())
     RequestConfig(request).configure(lessons_table)
 
     context['lessons_table'] = lessons_table
@@ -114,17 +114,21 @@ def lessons_day(request: HttpRequest, when: Optional[str] = None) -> HttpRespons
 
     return render(request, 'chronos/lessons_day.html', context)
 
+
 @admin_required
 def edit_substitution(request: HttpRequest, id_: int, week: int) -> HttpResponse:
     context = {}
 
     lesson_period = get_object_or_404(LessonPeriod, pk=id_)
 
-    lesson_substitution = LessonSubstitution.objects.filter(week=week, lesson_period=lesson_period).first()
+    lesson_substitution = LessonSubstitution.objects.filter(
+        week=week, lesson_period=lesson_period).first()
     if lesson_substitution:
-        edit_substitution_form = LessonSubstitutionForm(request.POST or None, instance=lesson_substitution)
+        edit_substitution_form = LessonSubstitutionForm(
+            request.POST or None, instance=lesson_substitution)
     else:
-        edit_substitution_form = LessonSubstitutionForm(request.POST or None, initial={'week': week, 'lesson_period': lesson_period})
+        edit_substitution_form = LessonSubstitutionForm(
+            request.POST or None, initial={'week': week, 'lesson_period': lesson_period})
 
     context['substitution'] = lesson_substitution