title: Convert Date to UTC timestamp in mysql
body: <p>I have a table with the following columns:</p>
  
  <pre><code>|start_date  |TZ      | 
  |Dec 2, 2012 |Eastern |
  |Dec 2, 2012 |GMT     |
  </code></pre>
  
  <p>Note 1: our server is in UTC time.  </p>
  
  <p>Note 2:The column start_date is a date field, not a timestamp field.  Dec 2nd 2012 implicitly means "2012-12-02 00:00:00"</p>
  
  <p>Note 3: The above table is actually multiple normalized tables, but for simplicity, I de-normalized it.</p>
  
  <p>Note 4: I can put anything into the TZ table to make this easy.</p>
  
  <p>I would like to <code>select from my_table where start_date &lt;= now()</code></p>
  
  <p>However, this doesn't work because of timezone.  If the current date/time is
  Dec 1st Eastern at 9PM (which is Dec 2nd 1AM UTC), the above query will return both results,
  but I really only want the 2nd one.  This is further complicated by daylight savings.</p>
  
  <p>Ideally, I would like a query that does the following:</p>
  
  <pre><code>select * from my_table where convert_to_utc_timestamp(start_date,tz) &lt;= now()
  </code></pre>
  
  <p>The above method would convert start_date to a timestamp and then convert it to the right timezone.</p>
  
  <p>How would I do this in SQL?</p>