How to add multiple years to DateTimeIndex in Pandas

Question

I'd like to add multiple years to my date index in pandas, but have not been able to do so:

ts is a dataframe with a series and relevant dates. I would like to extend those dates by an additional several years in order to add other series for plotting/analysis.

ts.head()

date
2014-12-31         NaN
2015-12-31    0.617876
2016-12-31    0.472640
2017-12-31    0.426240
2018-12-31    0.297176
Name: BL-US, dtype: float64

I've tried

ts.index.union([ts.index[-1] + datetime.timedelta(years=x) for x in range(7)])

and received the following error:

TypeError: 'years' is an invalid keyword argument for new()

Any suggestions? Thank you!

Answer 1

You should use date_range:

ts.index.union(pd.date_range(ts.index[-1], periods=5, freq='Y'))

output:

DatetimeIndex(['2014-12-31', '2015-12-31', '2016-12-31', '2017-12-31',
               '2018-12-31', '2019-12-31', '2020-12-31', '2021-12-31',
               '2022-12-31'],
              dtype='datetime64[ns]', freq='A-DEC')

Answer 2

This possibly works:

ts.index.union([ts.index[-1] + pd.offsets.DateOffset(years=x) for x in range(5)])