Database Wrapper Design issue: No operator matches the given name and argument type(s)
You'll need to explicitly convert your datetime strings to appropriate data types. Since you chose not to include the SQL statement in question, I can only guess what it's like, but if it looks anything like

...WHERE timestamp_column &gt; ?...


you'll need to replace it with 

...WHERE timestamp_column &gt; TO_TIMESTAMP(?, 'YYYY-MM-DD HH24:MI:SS')...


using, of course, an appropriate format string.