diff --git a/server/users/licenses.py b/server/users/licenses.py
index 57447d7c..4ec25f5c 100644
--- a/server/users/licenses.py
+++ b/server/users/licenses.py
@@ -9,7 +9,7 @@ MYSKILLBOX_LICENSES = {
     },
     "978-3-0355-1860-3": {
         'edition': STUDENT_KEY,
-        'duration': 455,
+        'duration': 365,
         'name': 'Student 1 year'
     },
     "978-3-0355-1862-7": {
@@ -24,7 +24,7 @@ MYSKILLBOX_LICENSES = {
     },
     "978-3-0355-1823-8": {
         'edition': TEACHER_KEY,
-        'duration': 455,
+        'duration': 365,
         'name': 'Teacher 1 year'
     }
 }
diff --git a/server/users/management/commands/__init__.py b/server/users/management/commands/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/server/users/management/commands/reset_license_duration.py b/server/users/management/commands/reset_license_duration.py
index 61f21402..9b66f3d5 100644
--- a/server/users/management/commands/reset_license_duration.py
+++ b/server/users/management/commands/reset_license_duration.py
@@ -1,11 +1,21 @@
+import json
+from datetime import datetime, date
+
 from django.utils.timezone import now
 from django.core.management.base import BaseCommand
 
+from users.licenses import MYSKILLBOX_LICENSES
 from users.models import License
 
+YEARLY_ISBNS = ["978-3-0355-1860-3", "978-3-0355-1823-8"]
+LONGER_DURATION = 455
+
 
 class Command(BaseCommand):
-    help = 'Reset licenses that have a duration that is longer than the standard duration'
+    help = """
+    Reset licenses that have a duration of one year
+    Uses the duration of MYSKILLBOX_LICENSES as reference.
+    """
 
     def add_arguments(self, parser):
         parser.add_argument('--dry-run', action='store_true', dest='save', default=False, help='Make dry-run')
@@ -14,4 +24,27 @@ class Command(BaseCommand):
         today = now().date()
 
         for license in License.objects.filter(expire_date__gte=today):
-            print(license)
+            isbn = license.get_isbn()
+            if isbn not in YEARLY_ISBNS:
+                continue
+
+            defined_duration = MYSKILLBOX_LICENSES[isbn]['duration']  # use isbn from hep due to our bug
+            start_date = license.get_hep_start_date()
+            duration_in_days = (license.expire_date - start_date).days
+            if duration_in_days == defined_duration:
+                continue
+
+            user_join_delta = (license.expire_date - license.licensee.date_joined.date()).days
+
+            if self._is_change_candidate(user_join_delta, duration_in_days, start_date):
+                print(license.id, duration_in_days, defined_duration, license.expire_date, start_date, user_join_delta)
+
+    def _is_change_candidate(self, user_join_delta: int, duration_in_days: int, start_date: date) -> bool:
+        """
+        user_join_delta == LONGER_DURATION: user joined the same number of days as the old duration was
+        duration_in_days == LONGER_DURATION: delta from start date and expiry date is the same as the old duration
+        start_date == NO_DATE: license does not have a start date -> was created after moving to new api as
+        such it the longer duration was set as duration
+        """
+        return user_join_delta == LONGER_DURATION or duration_in_days == LONGER_DURATION \
+               or start_date == License.NO_DATE
diff --git a/server/users/models.py b/server/users/models.py
index a6877966..794999d5 100644
--- a/server/users/models.py
+++ b/server/users/models.py
@@ -1,3 +1,4 @@
+import json
 import random
 import re
 import string
@@ -308,6 +309,8 @@ class License(models.Model):
 
     objects = LicenseManager()
 
+    NO_DATE = date(2011, 10, 7)  # used to tag licenses without start date
+
     def is_teacher_license(self):
         return self.for_role.key == RoleManager.TEACHER_KEY
 
@@ -315,6 +318,27 @@ class License(models.Model):
         date = make_aware(datetime(self.expire_date.year, self.expire_date.month, self.expire_date.day))
         return License.is_product_active(date, self.isbn)
 
+    def _read_as_json(self, raw_string: str) -> dict:
+        return json.loads(raw_string.replace("'", '"').replace('True', 'true').replace('False', 'false')
+                          .replace('None', 'null'))
+
+    def get_hep_start_date(self) -> date:
+        hep_data = self._read_as_json(self.raw)
+        if 'updated_at' in hep_data:  # old key from Magento. Format: 2020-06-22 18:45:13
+            date_string = hep_data['created_at']
+            return datetime.strptime(date_string, '%Y-%m-%d %H:%M:%S').date()
+
+        return License.NO_DATE
+
+    def get_isbn(self) -> str:
+        hep_data = self._read_as_json(self.raw)
+        if 'sku' in hep_data:  # Magento key
+            return hep_data['sku']
+        elif 'isbn' in hep_data:  # new shop key
+            return hep_data['isbn']
+        else:
+            return ''
+
     @staticmethod
     def is_product_active(expiry_date, isbn):
         now = timezone.now()