Problem to update record via function in Workflow

Problem to update record via function in Workflow

Dear All, 

I'm trying to update a date via function executed by workflow. The function you can see below.  


Cashflow_Datum = Verkaufdatum.addWeek(6);
response = zoho.crm.updateRecord('Deals',ID,Cashflow_Datum);

Always when I execute I'm getting following error: 

Funktion konnte nicht gespeichert werden
  • Argument type mismatches for the function zoho.crm.updaterecord at index 3 Line Number: 2

I have set following arguments.