This blog post provides a pieces of SQL which will look for Jobs in the SYS.DBA_JOBS view that appear to be Materialized View refreshes and display the timing information as well as the interval.
Execute the following SQL;
SUBSTR(SUBSTR(dj.what, 24, 255),
INSTR(SUBSTR(dj.what, 25, 255), '"')) VIEW_OWNER,
REPLACE(SUBSTR(SUBSTR(dj.what, 24, 255),
INSTR(SUBSTR(dj.what, 25, 255), '.') + 3,
FROM sys.dba_jobs dj
WHERE dj.what like 'dbms_refresh.refresh(''"%"."%"'');'
This will return something similar to;
This gives enough information to allow new views to be scheduled in the gaps around the refreshes of old views and I have always found very useful.