public async Task <IActionResult> Get(DateTime date)
        {
            if (date >= new DateTime(2015, 01, 01))
            {
                return(BadRequest(new ErrorResponse("Only dates up to the end of the year 2014 are allowed")));
            }
            else
            {
                var rates = await exchangeRateService.GetExchangeRateDifferences(date);

                return(new OkObjectResult(rates));
            }
        }