title: Postgres how to determine there are X records spanning 2 days of datetimes in a table
body: <p>I have a table containing electricity meter readings which looks something like this:</p>
  
  <pre><code>| meter_id | reading_interval_datetime |
  | 110      | 2018-01-15T00:00:00+00:00 |
  | 110      | 2018-01-15T00:30:00+00:00 |
  </code></pre>
  
  <p>The table is filled with at most 48 records per day (one reading every 30 mins).</p>
  
  <p>What's an efficient way to check if a particular meter has at least two days of readings in there?</p>