title: Extract time in getSymbols
body: <p>I want to extract the time for some stock market to fit tree model. For example these codes are for loading Nikkei Market data:</p>
  
  <pre><code>library(quantmod)
  library(zoo)
  symbols=c('^N225')
  getSymbols(symbols,src='yahoo', from="2003-04-28", to="2007-10-29")
  </code></pre>
  
  <p>After that, I want to extract the time that the market is work (we could see the time in the first left column of the market data after we write <code>N225</code>). when we save these data with csv format the time column is replaced with ID number.
  Someone say that use the zoo format and after I save the data with these code:</p>
  
  <pre><code>N&lt;-data.frame(N225)
  Ndata&lt;-read.zoo(N)
  </code></pre>
  
  <p>the warning has appeared as follow:</p>
  
  <pre><code>In zoo(rval, index(x)[i]) :
  some methods for “zoo” objects do not work if the index entries in ‘order.by’ are not unique
  </code></pre>
  
  <p>and when we write <code>Ndata</code> the time column is replaced with some number that is not the time. how can I extract the time?</p>