title: How can I increment a date in datetime64[ns] format by 6 calendar months?
body: <p>I never realised that incrementing a simple date in Python would be such an insurmountable challenge, but have given up after 2 hours of trying and searching on this forum. I have a dataframe with a column <code>effective_date</code>, which contains entries like <code>2019-01-02</code> and datatype <code>datetime64[ns]</code>.</p>
  <p>I've tried:</p>
  <pre><code>data['effective_date'] = pd.to_datetime(data['effective_date'].values)
  data['six_mth_interval'] = data['effective_date'].apply(lambda x: x['effective_date'].values + relativedelta(months=6))
  </code></pre>
  <p>... but I get the following error:</p>
  <pre><code>&lt;ipython-input-315-b81c59eb6b0d&gt; in &lt;lambda&gt;(x)
  ----&gt; 1 data['six_mth_interval'] = data['effective_date'].apply(lambda x: x['effective_date'] + relativedelta(months=6))
  
  TypeError: 'Timestamp' object is not subscriptable
  </code></pre>
  <p>Existing articles on S/O have not been helpful.</p>