pandas.Series.to_timestamp
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Series.to_timestamp(freq=None, how='start', copy=True)[source]
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Cast to datetimeindex of timestamps, at beginning of period Parameters: freq : string, default frequency of PeriodIndex Desired frequency how : {‘s’, ‘e’, ‘start’, ‘end’} Convention for converting period to timestamp; start of period vs. end Returns: ts : Series with DatetimeIndex 
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Licensed under the 3-clause BSD License.
    https://pandas.pydata.org/pandas-docs/version/0.20.3/generated/pandas.Series.to_timestamp.html