Shift the time index, using the index’s frequency if available.
Number of periods to move, can be positive or negative.
Increment to use from the tseries module
or time rule expressed as a string (e.g. ‘EOM’).
Corresponds to the axis that contains the Index.
If freq is not specified then tries to use the freq or inferred_freq
attributes of the index. If neither of those attributes exist, a
ValueError is thrown