Answer
That kind of dynamic-date token isn't reliable for Quick Report parameters used in an Application Server Task — it can produce errors like ORA-01841 rather than resolving to an actual date. Instead, build the dynamic date logic directly into the Quick Report's own SQL query, using something like NVL(TO_DATE('&from_date', 'DD/MM/YYYY'), TRUNC(SYSDATE)) for each date parameter — this lets the parameter default to the current date (or a calculated relative date) inside the query itself whenever the Application Server Task doesn't supply an explicit value, without depending on a token substitution mechanism that isn't designed for this context.