Instead of adding an earlier suggested Data Conversion you can cast the nvarchar column to a varchar column. This prevents you from having an unnecessary step and has a higher performance then the alternative.
In the select of your SQL statement replace date
with CAST(date AS varchar([size]))
. For some reason this does not yet change the output data type. To do this do the following:
After doing this your source data will be output as a varchar and your error will disappear.