diff --git a/custom_components/ecowater_softener/coordinator.py b/custom_components/ecowater_softener/coordinator.py
index 96e1639..315592d 100644
--- a/custom_components/ecowater_softener/coordinator.py
+++ b/custom_components/ecowater_softener/coordinator.py
@@ -58,7 +58,9 @@ async def _async_update_data(self):
             if str(data_json['out_of_salt']).lower() == 'today':
                 data[OUT_OF_SALT_ON] = datetime.today().strftime('%Y-%m-%d')
             elif str(data_json['out_of_salt']).lower() == 'tomorrow':
-                data[OUT_OF_SALT_ON] = (datetime.today() + datetime.timedelta(days=1)).strftime('%Y-%m-%d')
+                data[OUT_OF_SALT_ON] = (datetime.today() + timedelta(days=1)).strftime('%Y-%m-%d')
+            elif str(data_json['out_of_salt']).lower() == 'yesterday':
+                data[OUT_OF_SALT_ON] = (datetime.today() - timedelta(days=1)).strftime('%Y-%m-%d')
             # Runs correct datetime.strptime() depending on date format entered during setup.
             elif self._dateformat == "dd/mm/yyyy":
                 data[OUT_OF_SALT_ON] = datetime.strptime(data_json['out_of_salt'], '%d/%m/%Y').strftime('%Y-%m-%d')
@@ -80,4 +82,4 @@ async def _async_update_data(self):
             
             return data
         except Exception as e:
-            raise UpdateFailed(f"Error communicating with API: {e}")
\ No newline at end of file
+            raise UpdateFailed(f"Error communicating with API: {e}")