diff --git a/aosstower/level_b1/nc.py b/aosstower/level_b1/nc.py
index 894ee37652bb882dd89b4601e9dcc579f3f8c58d..8d7df816ba407958b85e93739337d2ba04ef28d7 100644
--- a/aosstower/level_b1/nc.py
+++ b/aosstower/level_b1/nc.py
@@ -8,6 +8,7 @@ from netCDF4 import Dataset
 import numpy as np 
 import platform
 from aosstower import station
+from datetime import timedelta as delta
 
 LOG = logging.getLogger(__name__)
 
@@ -118,7 +119,7 @@ def createVariables(ncFile, firstStamp, chunksizes, zlib):
     return ncFile
 
 def minuteAverages(frame):
-    frame['minute'] = [ts.replace(second=0) for ts in frame.index]
+    frame['minute'] = [(ts + delta(minutes=1)).replace(second=0) for ts in frame.index]
     newFrame = frame.groupby('minute').mean()
     newFrame.index.names = ['']
     
@@ -129,6 +130,8 @@ def minuteAverages(frame):
     if 'wind_direction' in columns:
         del newFrame['wind_direction']
 
+    print(frame)
+   
     del frame['minute']
 
     return newFrame.fillna(-99999)