# pandas.DatetimeIndex.to_period

`DatetimeIndex.``to_period`(*args, **kwargs)

  Cast to PeriodArray/Index at a particular frequency.

  Converts DatetimeArray/Index to PeriodArray/Index.

  Parameters:

  freq : str or Offset, optional

  > One of pandas’ offset strings or an Offset object. Will be inferred by default.

  Returns: | PeriodArray/Index

  Raises:

  ValueError

  > When converting a DatetimeArray/Index with non-regular values, so that a frequency cannot be inferred.

  See also

  `PeriodIndex`
    Immutable ndarray holding ordinal values.
  `DatetimeIndex.to_pydatetime`
    Return DatetimeIndex as object.

  Examples

      >>> df = pd.DataFrame({"y": [1, 2, 3]},
      ...                   index=pd.to_datetime(["2000-03-31 00:00:00",
      ...                                         "2000-05-31 00:00:00",
      ...                                         "2000-08-31 00:00:00"]))
      >>> df.index.to_period("M")
      PeriodIndex(['2000-03', '2000-05', '2000-08'],
                  dtype='period[M]', freq='M')

  Infer the daily frequency

      >>> idx = pd.date_range("2017-01-01", periods=2)
      >>> idx.to_period()
      PeriodIndex(['2017-01-01', '2017-01-02'],
                  dtype='period[D]', freq='D')

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