src/HOL/Tools/Nitpick/kodkod.ML

                  commas (map int_string_for_bound int_bounds) ^ "\n"));
          map (fn b => (out_assign b; out ";")) expr_assigns;
          out "solve "; out_outmost_f formula; out ";\n")
   in
     out ("// This file was generated by Isabelle (most likely Nitpick)\n" ^
-         "// " ^ Date.fmt "%Y-%m-%d %H:%M:%S"
-                          (Date.fromTimeLocal (Time.now ())) ^ "\n");
+         "// " ^ Sledgehammer_Util.timestamp () ^ "\n");
     map out_problem problems
   end
 
 (** Parsing of solution **)