title: how to read date and time on ecmwf file
body: <p>I have global datasets in netcdf file. Time information on data file is: </p>
  
  <pre><code>&lt;type 'netCDF4._netCDF4.Variable'&gt;
  int32 time(time)
      units: hours since 1900-01-01 00:00:0.0
      long_name: time
      calendar: gregorian
  unlimited dimensions: time
  current shape = (5875,)
  filling off
  </code></pre>
  
  <p>when I extracted time from file, I got this array:</p>
  
  <pre><code>array([ 876600,  876624,  876648, ..., 1017528, 1017552, 1017576], dtype=int32) 
  </code></pre>
  
  <p>my question is how to convert this array into proper date format?
  [Note: This is a daily data sets and number in an array is corresponding to an hours from 1900-01-01]</p>