I have a few Materialized Views that I need to update weekly and monthly.

So for the weekly I'm using:

Code:
execute DBMS_REFRESH.MAKE(
name=>'LPMVRefresh_Weekly_1',
list=>'mySchema.MV1_mv,mySchema.MV2_mv',
next_date => TO_DATE('2013-09-08:00:30:00','YYYY-MM-DD:HH24:MI:SS'),
interval =>'sysdate+7');
How can I do so they refresh monthly, say every 1st of the month at 1 am? Is there something like Interval => sysdate+monthly?