When dealing with time series, there are two main concepts that you have to consider: points in time ranges, and time spans. In pandas, the former is represented by the Timestamp datatype, which is equivalent to the Python datatime.datetime (datetime) datatype and is interchangeable with it. The latter (time span) is represented by the Period datatype, which is specific to pandas.

Each of these datatypes has index datatypes associated with them: DatetimeIndex for Timestamp/Datetime and PeriodIndex for Period. These index datatypes are basically subtypes of numpy.ndarray that contain the corresponding Timestamp and Period datatypes and can be used as indexes for the Series and DataFrame objects.