anchor.diff:  	{_,  {struct, VFObj}} = lists:keyfind("validFor", 1, Price),
   	{_, SDT} = lists:keyfind("startDateTime", 1, VFObj),
   	{_, EDT} = lists:keyfind("endDateTime", 1, VFObj),
  -	{ocs_rest:timestamp(SDT), ocs_rest:timestamp(EDT)};
  +	{ocs_rest:iso8601(SDT), ocs_rest:iso8601(EDT)};
   prod_price_vf(json, Price) ->
   	{SDateTime, EDateTime} = Price#price.valid_for,
   	SDT = {"startDateTime", ocs_rest:iso8601(SDateTime)},
  
positive.code: 	{_, {struct, VFObj}} = lists:keyfind("validFor", 1, Product),
  	{_, SDT} = lists:keyfind("startDateTime", 1, VFObj),
  	{_, EDT} = lists:keyfind("endDateTime", 1, VFObj),
  	{ocs_rest:timestamp(SDT), ocs_rest:timestamp(EDT)};
  prod_vf(json, Product) ->
  	case Product#product.valid_for of
  		{SDateTime, undefined} ->
  
negative.code: 		%ProdValidity = validity_period(ProdSTime, ProdETime),
  		if
  			Price#price.alteration == undefined ->
  				Price1 = {struct, [Name, Description, ValidFor,
  					PriceType, PriceObj, UOMeasure, RCPeriod]},
  				po_price(json, T, [Price1 | Prices]);
  			true ->
  