title: Rounding a pandas.DatetimeIndex from [ns] to [s]
body: <p>So I have dataframe with this index</p>
  
  <pre><code>print df.index
  </code></pre>
  
  <p>result:</p>
  
  <pre><code>&lt;class 'pandas.tseries.index.DatetimeIndex'&gt;
  [2000-01-01 11:30:16.624989600, ..., 2000-01-01 11:50:33.124011100]
  Length: 240178, Freq: None, Timezone: None
  </code></pre>
  
  <p>And I want to round seconds to for example:</p>
  
  <pre><code>&lt;class 'pandas.tseries.index.DatetimeIndex'&gt;
  [2000-01-01 11:30:16.625, ..., 2000-01-01 11:50:33.124]
  Length: 240178, Freq: None, Timezone: None
  </code></pre>
  
  <p>Or</p>
  
  <pre><code>&lt;class 'pandas.tseries.index.DatetimeIndex'&gt;
  [2000-01-01 11:30:16.625000000, ..., 2000-01-01 11:50:33.124000000]
  Length: 240178, Freq: None, Timezone: None
  </code></pre>
  
  <p>So I am using <code>datetimeindex.round()</code> method</p>
  
  <pre><code>print df.index.round(decimals=3)
  </code></pre>
  
  <p>with such result:</p>
  
  <pre><code>TypeError
  Traceback (most recent call last) &lt;ipython-input-9-6e2dbd74ae75&gt; in &lt;module&gt;()
        1 print df.index
  ----&gt; 2 print df.index.round(decimals=3) TypeError: ufunc multiply cannot use operands with types dtype('&lt;M8[ns]') and dtype('float64')
  </code></pre>
  
  <p>Is that method simply not available yet?</p>
  
  <p>EDIT:</p>
  
  <pre><code>pd.show_versions()
  
  INSTALLED VERSIONS
  ------------------
  commit: None
  python: 2.7.6.final.0
  python-bits: 64
  OS: Windows
  OS-release: 7
  machine: AMD64
  processor: Intel64 Family 6 Model 37 Stepping 2, GenuineIntel
  byteorder: little
  LC_ALL: None
  LANG: None
  
  pandas: 0.14.0
  nose: 1.3.1
  Cython: 0.20.1
  numpy: 1.8.1
  scipy: 0.13.3
  statsmodels: 0.5.0
  IPython: 2.0.0
  sphinx: 1.2.2
  patsy: 0.2.1
  scikits.timeseries: None
  dateutil: 2.2
  pytz: 2013.9
  bottleneck: None
  tables: 3.1.1
  numexpr: 2.3.1
  matplotlib: 1.3.1
  openpyxl: None
  xlrd: 0.9.3
  xlwt: 0.7.5
  xlsxwriter: None
  lxml: None
  bs4: None
  html5lib: None
  bq: None
  apiclient: None
  rpy2: None
  sqlalchemy: 0.9.4
  pymysql: None
  psycopg2: None
  </code></pre>