Conversion failed when converting datetime from character string.
i m getting this error while inserting values in the DB from my application
i have done insertion before too , but i never receive this strange error but when
i insert the same thing manually then i didn't get this error
how to solve this error
the format i used is also yyyy-mm-dd
then how to solve this error?????????

I have stopped relying on good faith in MSSQL to do string to DATE conversions. Do an explicit CONVERT
If it has always worked until now, your application may have fed it some flawed data. Check if the format is really YYYY-MM-DD. Print the string you pass to MSSQL (log file, screen, ...), to be 100% sure.