title: Get timestamp of one month ago in PostgreSQL
body: <p>I have a PostgreSQL database in which one table rapidly grows very large (several million rows every month or so) so I'd like to periodically archive the contents of that table into a separate table.</p>
  
  <p>I'm intending to use a cron job to execute a .sql file nightly to archive all rows that are older than one month into the other table.</p>
  
  <p>I have the query working fine, but I need to know how to dynamically create a timestamp of one month prior.</p>
  
  <p>The <code>time</code> column is stored in the format <code>2013-10-27 06:53:12</code> and I need to know what to use in an SQL query to build a timestamp of exactly one month prior. For example, if today is October 27, 2013, I want the query to match all rows where time &lt; <code>2013-09-27 00:00:00</code></p>