We have analyzed your query with the provided code.We are unable to reproduce the specified issue.We would like to let you know that, the value which you are passing will be set to the datepicker control.So, please ensure the value passed for the datepicker control from the code-behind.We have prepared the sample to display the datepicker control with Spanish dateformat.Please find the sample under the following location,
Could you please check with the above sample? If still you face the same problem, please revert us by modifying the sample based on your application along with replication procedure. This would be helpful for us to serve you.
Please let us know if you have further queries.