There's not enough information on your post to give you a real answer.

We can't see your data.

However, I would recommend you to examine this:

select

CONVERT(varchar(30),clx.prdt) as ADate

from EXPM clx where clx.prdt<>0

Or this

select

CONVERT(varchar(30),clx.prdt) as ADate

from EXPM clx where clx.prdt<>0

AND ISDATE(CONVERT(varchar(30),clx.prdt)) = 0