diff --git a/combine_files.py b/combine_files.py
index 819dcf0..f971ad3 100644
--- a/combine_files.py
+++ b/combine_files.py
@@ -31,15 +31,22 @@ def cleanRow(row):
 for listing in raw_files:
     print(listing)
     if os.path.isfile(listing):
-        file_date = re.match('.*([0-9]{8}).*csv$', listing).group(1)
-        with open(listing) as csvfile:
-            spamreader = csv.reader(csvfile)
-            data = []
-            for row in spamreader:
-                row = cleanRow(row)
-                data.append(dict(zip(header, row)))
-
-            full_data[file_date] = data
+        # Updated regex to match 'M.YYYY' format in the filename
+        match = re.match(r'.*([0-9]{1,2}\.[0-9]{4}).*\.csv$', listing)
+        
+        # Check if match exists before accessing group(1) to avoid AttributeError
+        if match:  # Updated conditional check to prevent errors
+            file_date = match.group(1)
+            with open(listing) as csvfile:
+                spamreader = csv.reader(csvfile)
+                data = []
+                for row in spamreader:
+                    row = cleanRow(row)
+                    data.append(dict(zip(header, row)))
+
+                full_data[file_date] = data
+        else:
+            print(f"Warning: No valid date found in filename '{listing}'")  # Added warning message
 
 with open(combined_file, 'w') as jsonFile:
     json.dump(full_data, jsonFile, indent=4)