How to fix error An object reference is required for the non-static field, method, or property 'System.DateTime.ToShortTimeString()'

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 To fix the error:
An object reference is required for the non-static field, method, or property 'System.DateTime.ToShortTimeString()'  

Replace
   string d = DateTime.ToShortDateString();
   string t = DateTime.ToShortTimeString();
With
  string d = DateTime.Today.ToShortDateString();
  string t = DateTime.Now.ToShortTimeString();