Fun with Dates

Greetings,<br /><br /> I want to be able to select all data going back to the beginning of the current month.  The
followingportion of an SQL does NOT work, but more or less describes what I want...<br /><br /> ... WHERE obstime >=
NOW()- INTERVAL (SELECT EXTRACT (DAY FROM NOW() ) ) + ' days'<br /><br /> In other words, if today is the 29th of the
month,I want to select data that is within 29 days old... WHERE obstime >= NOW() - INTERVAL '29 days'<br /><br />
Howdo I craft a query to do use a variable day of the month?<br /><br /> Mark<br />