diff --git a/changehc/delphi_changehc/backfill.py b/changehc/delphi_changehc/backfill.py
index 8b9ea8491..7338c4c40 100644
--- a/changehc/delphi_changehc/backfill.py
+++ b/changehc/delphi_changehc/backfill.py
@@ -46,6 +46,18 @@ def store_backfill_file(df, _end_date, backfill_dir, numtype, geo, weekday):
                         'num', 'den']
     backfilldata = backfilldata.loc[backfilldata["time_value"] >= _start_date,
                                     selected_columns]
+
+    backfilldata["lag"] = [(_end_date - x).days for x in backfilldata["time_value"]]
+    backfilldata["time_value"] = backfilldata.time_value.dt.strftime("%Y-%m-%d")
+    backfilldata["issue_date"] = datetime.strftime(_end_date, "%Y-%m-%d")
+
+    backfilldata = backfilldata.astype({
+        "time_value": "string",
+        "issue_date": "string",
+        "fips": "string",
+        "state_id": "string"
+    })
+
     path = backfill_dir + \
         "/changehc_%s_as_of_%s.parquet"%(numtype, datetime.strftime(_end_date, "%Y%m%d"))
     # Store intermediate file into the backfill folder
@@ -109,9 +121,6 @@ def get_date(file_link):
     pdList = []
     for fn in new_files:
         df = pd.read_parquet(fn, engine='pyarrow')
-        issue_date = get_date(fn)
-        df["issue_date"] = issue_date
-        df["lag"] = [(issue_date - x).days for x in df["time_value"]]
         pdList.append(df)
     merged_file = pd.concat(pdList).sort_values(["time_value", "fips"])
     path = backfill_dir + "/changehc_%s_from_%s_to_%s.parquet"%(
diff --git a/changehc/tests/test_backfill.py b/changehc/tests/test_backfill.py
index 58e76b9db..c7c8796d4 100644
--- a/changehc/tests/test_backfill.py
+++ b/changehc/tests/test_backfill.py
@@ -40,7 +40,7 @@
 class TestBackfill:
     
     def test_store_backfill_file(self):
-        
+
         fn = "changehc_covid_as_of_20200101.parquet"
         dropdate = datetime(2020, 1, 1)
         numtype = "covid"
@@ -69,7 +69,7 @@ def test_store_backfill_file(self):
         backfill_df = pd.read_parquet(backfill_dir + "/"+ fn, engine='pyarrow')
         
         selected_columns = ['time_value', 'fips', 'state_id',
-                        'num', 'den']
+                        'num', 'den', 'lag', 'issue_date']
         assert set(selected_columns) == set(backfill_df.columns)  
         
         os.remove(backfill_dir + "/" + fn)
@@ -114,9 +114,6 @@ def test_merge_backfill_file(self):
             if "from" in file:
                 continue
             df = pd.read_parquet(file, engine='pyarrow')
-            issue_date = datetime.strptime(file[-16:-8], "%Y%m%d")
-            df["issue_date"] = issue_date
-            df["lag"] = [(issue_date - x).days for x in df["time_value"]]
             pdList.append(df)
             os.remove(file)
         new_files = glob.glob(backfill_dir + "/changehc_%s*.parquet"%numtype)
diff --git a/quidel_covidtest/delphi_quidel_covidtest/backfill.py b/quidel_covidtest/delphi_quidel_covidtest/backfill.py
index 7e8482551..1c83622ea 100644
--- a/quidel_covidtest/delphi_quidel_covidtest/backfill.py
+++ b/quidel_covidtest/delphi_quidel_covidtest/backfill.py
@@ -56,6 +56,17 @@ def store_backfill_file(df, _end_date, backfill_dir):
                         'num_age_0_17', 'den_age_0_17']
     backfilldata = backfilldata.loc[backfilldata["time_value"] >= _start_date,
                                     selected_columns]
+    backfilldata["lag"] = [(_end_date - x).days for x in backfilldata["time_value"]]
+    backfilldata["time_value"] = backfilldata.time_value.dt.strftime("%Y-%m-%d")
+    backfilldata["issue_date"] = datetime.strftime(_end_date, "%Y-%m-%d")
+
+    backfilldata = backfilldata.astype({
+        "time_value": "string",
+        "issue_date": "string",
+        "fips": "string",
+        "state_id": "string"
+    })
+
     path = backfill_dir + \
         "/quidel_covidtest_as_of_%s.parquet"%datetime.strftime(_end_date, "%Y%m%d")
     # Store intermediate file into the backfill folder
@@ -108,9 +119,6 @@ def get_date(file_link):
     pdList = []
     for fn in new_files:
         df = pd.read_parquet(fn, engine='pyarrow')
-        issue_date = get_date(fn)
-        df["issue_date"] = issue_date
-        df["lag"] = [(issue_date - x).days for x in df["time_value"]]
         pdList.append(df)
     merged_file = pd.concat(pdList).sort_values(["time_value", "fips"])
     path = backfill_dir + "/quidel_covidtest_from_%s_to_%s.parquet"%(
diff --git a/quidel_covidtest/tests/test_backfill.py b/quidel_covidtest/tests/test_backfill.py
index 7a033fb47..27e0d01bc 100644
--- a/quidel_covidtest/tests/test_backfill.py
+++ b/quidel_covidtest/tests/test_backfill.py
@@ -49,7 +49,8 @@ def test_store_backfill_file(self):
                         'num_age_18_49', 'den_age_18_49',
                         'num_age_50_64', 'den_age_50_64',
                         'num_age_65plus', 'den_age_65plus',
-                        'num_age_0_17', 'den_age_0_17']
+                        'num_age_0_17', 'den_age_0_17',
+                        'lag', 'issue_date']
         assert set(selected_columns) == set(backfill_df.columns)  
         
         os.remove(backfill_dir + "/" + fn)
@@ -86,9 +87,6 @@ def test_merge_backfill_file(self):
             if "from" in file:
                 continue
             df = pd.read_parquet(file, engine='pyarrow')
-            issue_date = datetime.strptime(file[-16:-8], "%Y%m%d")
-            df["issue_date"] = issue_date
-            df["lag"] = [(issue_date - x).days for x in df["time_value"]]
             pdList.append(df)
             os.remove(file)
         new_files = glob.glob(backfill_dir + "/quidel_covidtest*.parquet")