diff --git a/perdiem.py b/perdiem.py
index f341807..7fac2fc 100644
--- a/perdiem.py
+++ b/perdiem.py
@@ -1,12 +1,14 @@
 import os
 import logging
 from datetime import datetime
+from dateutil.relativedelta import relativedelta
+
 from pyutl.sendmail import SendMail
 from pyutl.localenv import localenv
 localenv.load()
 
 HOME_DIR = os.path.dirname(os.path.abspath(__file__))
-THIS_MONTH = datetime.now().strftime("%m%Y")
+THIS_MONTH = (datetime.now() + relativedelta(months=-1)).strftime("%m%Y")
 FILE = [os.path.join(HOME_DIR, f'viatico_{THIS_MONTH}.xlsx')]
 LOG_FILE = os.path.join(HOME_DIR, 'perdiem.log')