Legacy app not working with newer PG, is there a quick fix?

I have a legacy client java application that I try to run against a new Postgres server.
All data migrates as expected. Everything seems to work ok, except for one thing.

ERROR:  function to_date(timestamp without time zone, unknown) does not exist at character 9
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.

The application was written with and works with PG 8.2.3

I understand that from PG 8.3 explicit typecasting is necessary, like:
to_date(cast(createddate as TEXT),'YYYY-MM-DD’)

But I do not have access to the source code. Is there a way to go around this, by creating a macro & function to
providethe type cast on the server side. 
Without having to change anything in the client application?

/Lars