In [1]: dates = pd.period_range('01-Jan-2015', '01-Jan-2016', freq='M') ...: series = pd.TimeSeries(np.arange(dates.size), dates) ...: In [2]: series Out[2]: 2015-01 0 2015-02 1 2015-03 2 2015-04 3 2015-05 4 2015-06 5 2015-07 6 2015-08 7 2015-09 8 2015-10 9 2015-11 10 2015-12 11 2016-01 12 Freq: M, dtype: int32 In [3]: series.index += 1 In [4]: series Out[4]: 541 0 542 1 543 2 544 3 545 4 546 5 547 6 548 7 549 8 550 9 551 10 552 11 553 12 dtype: int32 In [5]: series.index Out[5]: Int64Index([541, 542, 543, 544, 545, 546, 547, 548, 549, 550, 551, 552, 553], dtype='int64') In [6]: pd.__version__ Out[6]: '0.13.1-339-g6c3755b'