diff --git a/tools/RAiDER/gnss/processDelayFiles.py b/tools/RAiDER/gnss/processDelayFiles.py
index bb1b87661..bd80c829e 100644
--- a/tools/RAiDER/gnss/processDelayFiles.py
+++ b/tools/RAiDER/gnss/processDelayFiles.py
@@ -122,10 +122,9 @@ def update_time(row, localTime_hrs):
 
 def pass_common_obs(reference, target, localtime=None):
     '''Pass only observations in target spatiotemporally common to reference'''
-    if isinstance(target['Datetime'][0], 'str'):
+    if isinstance(target['Datetime'].iloc[0], str):
         target['Datetime'] = target['Datetime'].apply(lambda x:
-                                                      datetime.datetime.strptime(x, '%Y-%m-%d %H:%M:%S')
-                                                     )
+                          datetime.datetime.strptime(x, '%Y-%m-%d %H:%M:%S'))
     if localtime:
         return target[target['Datetime'].dt.date.isin(reference['Datetime']
                       .dt.date) &