diff --git a/src/EcoFOCIpy/io/wetlabs_parser.py b/src/EcoFOCIpy/io/wetlabs_parser.py
index c8521f8..fd9cace 100644
--- a/src/EcoFOCIpy/io/wetlabs_parser.py
+++ b/src/EcoFOCIpy/io/wetlabs_parser.py
@@ -13,9 +13,9 @@
 """
 import sys
 
+import datetime
 import pandas as pd
 
-
 class wetlabs(object):
     r""" Wetlabs Unified parser
     
@@ -117,7 +117,7 @@ def lineartimecorr(x,deltaT,T0) :
                 return date
 
             T0 = self.rawdata_df.index[0]
-            deltaT = offset / (self.rawdata_df.index[-1] - T0)
+            deltaT = datetime.timedelta(seconds=offset) / (self.rawdata_df.index[-1] - T0)
 
             self.rawdata_df.index = self.rawdata_df.reset_index().apply(lambda x: lineartimecorr(x.date_time,deltaT,T0), axis=1)