Sort a column by date

Hello everyone,

I would like to be able to sort a date column in clicking on the title. I follow this tutorial but it doesn't work. I can click on the column title (the last one), but the order is wrong.

The format date is DD/MM/YYYY.

I implement it in this fiddle.

Could you please tell me what I did wrong please?

Thank you for your help,
Lionet