Unable to pass URL params into api request - ruby-on-rails

Question

I'm working with the Bing API and when I am making a SOAP request to acquire my campaign stats I'm having trouble passing URL params for date (provided by bootstrap datepicker) to the request.
I keep receiving the following error -
(a:DeserializationFailed) The formatter threw an exception while trying to deserialize the message: There was an error while trying to deserialize parameter https://adcenter.microsoft.com/v8:ReportRequest. The InnerException message was 'There was an error deserializing the object of type Microsoft.AdCenter.Advertiser.Reporting.Api.DataContracts.Request.ReportRequest. The value '' cannot be parsed as the type 'Int32'.'. Please see InnerException for more details.
It seems to me as though it is not able to receive the values I have set as the start/end date in the params. It is working when the params[:start]/[:end] values are nil
Here is the controller code setting up the date params (datepicker works fine for all other requests):
#Start Bing Reporting Code - set date for request ID
if params[:start].nil?
bing_start_date = DateTime.parse((Date.today - 7).to_s).strftime("%Y-%m-%d")
yearstart = bing_start_date[0,4]
monthstart = bing_start_date[5..6]
daystart = bing_start_date[8..9]
bing_end_date = DateTime.parse((Date.today - 1).to_s).strftime("%Y-%m-%d")
yearend = bing_end_date[0,4]
monthend = bing_end_date[5..6]
dayend = bing_end_date[8..9]
else
bing_start_date = params[:start]
yearstart = bing_start_date[2,4]
monthstart = bing_start_date[5..6]
daystart = bing_start_date[8..9]
bing_end_date = params[:end]
yearend = bing_end_date[2,4]
monthend = bing_end_date[5..6]
dayend = bing_end_date[8..9]
end
Here is the SOAP request body where I set the custom date range (using Savon gem):
soap.body = "<CustomDateRangeEnd i:nil=\"false\"><Day>#{dayend}</Day><Month>#{monthend}</Month><Year>#{yearend}</Year></CustomDateRangeEnd><CustomDateRangeStart i:nil=\"false\"><Day>#{daystart}</Day><Month>#{monthstart}</Month><Year>#{yearstart}</Year></CustomDateRangeStart></Time></ReportRequest>"
It works fine If I just set the yearend/start, monthend/start, dayend/start variables manually like so:
yearstart = '2014'
monthstart = '01'
daystart = '01'
#this would set the start date properly to Jan 1 2014

Answer 1

Foolish mistake. I used the same start index/length and ranges for the 'if' statement as I did for the 'else'. As a result it was throwing and empty string to <day>
The date output for the 'if' was "2014-01-13" and the output for the else was "20140113"
Therefore, I needed to adjust the index/length and ranges like so:
bing_start_date = params[:start]
yearstart = bing_start_date[0,4]
monthstart = bing_start_date[4..5]
daystart = bing_start_date[6..7]