diff --git a/DataTree/AcquiredData/DataFiles/FileClass.m b/DataTree/AcquiredData/DataFiles/FileClass.m
index ea2e1f23..8118f7a6 100644
--- a/DataTree/AcquiredData/DataFiles/FileClass.m
+++ b/DataTree/AcquiredData/DataFiles/FileClass.m
@@ -90,7 +90,7 @@ function Add(obj, obj2)
             obj.name         = getPathRelative(rootpath, obj2.rootdir);
             obj.rootdir 	 = obj2.rootdir;
             obj.date         = obj2.date;
-            obj.datenum      = datestr2datenum(obj.date);
+            obj.datenum      = obj2.datenum;
             if obj.IsFile()
                 obj.err          = obj.errcodeUnvalidated;          % Set error to unvalidated
             else
@@ -622,4 +622,4 @@ function SetErrorUnvalidated(obj)
         
     end
   
-end
\ No newline at end of file
+end