diff --git a/api/core/data/processing/filling.py b/api/core/data/processing/filling.py
index 6c1ec3ba9c2a372ba78b207e9d7b0ec46c86d814..991b9c5132d1d7c2926e4dac83d3faa4ebe969dc 100644
--- a/api/core/data/processing/filling.py
+++ b/api/core/data/processing/filling.py
@@ -35,8 +35,8 @@ class Filling:
             for m in missing_dates:
                 v = {
                     "sampling_point_id": key,
-                    "begin_position": pd.to_datetime(datetime.fromtimestamp(m-ts_timestep).strftime('%Y-%m-%dT%H:%M:%S')+tz, format="%Y-%m-%dT%H:%M:%S%Z"),
-                    "end_position": pd.to_datetime(datetime.fromtimestamp(m).strftime('%Y-%m-%dT%H:%M:%S')+tz, format="%Y-%m-%dT%H:%M:%S%Z"),
+                    "begin_position": pd.to_datetime(datetime.utcfromtimestamp(m).strftime('%Y-%m-%dT%H:%M:%S')+tz, format="%Y-%m-%dT%H:%M:%S%Z"), 
+                    "end_position": pd.to_datetime(datetime.utcfromtimestamp(m+ts_timestep).strftime('%Y-%m-%dT%H:%M:%S')+tz, format="%Y-%m-%dT%H:%M:%S%Z"),
                     "value": -9900,
                     "verification_flag": 3,
                     "validation_flag": -1,