Feature request: Add annual offset that is not anchored

[rs2]

Code Sample, a copy-pastable example if possible

pd.bdate_range(end='today', periods=2, freq='1A').freq.name
# Prints 'A-DEC'
pd.bdate_range(end='today', periods=2, freq='1A')[0].date()
# prints datetime.date(2015, 12, 31)

Problem description

Pandas divides offsets into regular and anchored (see Offset aliases).

There are regular aliases for any frequency but annual. A typical use case - give me a bdate_range with dates spaced 1 year apart ending today. 12M and 52W are only proxies, but won't give the exact expected result.

Expected Output

pd.bdate_range(end='2017-03-12', periods=2, freq='1A-actual-for-real')[0].date() # Saturday
# prints datetime.date(2016, 3, 11) # Friday

Output of pd.show_versions()

pandas: 0.19.2

[chris-b1]

There could be a better API, or at minimum better docs, but you can accomplish this with a DateOffset.

In [216]: pd.date_range(end='2017-03-12', periods=12, freq=pd.DateOffset(years=1))
Out[216]: 
DatetimeIndex(['2006-03-12', '2007-03-12', '2008-03-12', '2009-03-12',
               '2010-03-12', '2011-03-12', '2012-03-12', '2013-03-12',
               '2014-03-12', '2015-03-12', '2016-03-12', '2017-03-12'],
              dtype='datetime64[ns]', freq='<DateOffset: kwds={'years': 1}>')

[rs2]

@chris-b1 2016-03-12 is a Saturday, whereas bdate_range is expected to yield at least Mon-Fri?

[chris-b1]

Oh, one to to note is that bdate_range is just an alias for date_range with freq='B', it doesn't do anything special with other offsets.

Getting hackier, but I think this would work?

pd.date_range(end='2017-03-12', periods=12, freq=pd.DateOffset(years=1)) + pd.offsets.BusinessDay(n=0)

Out[225]: 
DatetimeIndex(['2006-03-13', '2007-03-12', '2008-03-12', '2009-03-12',
               '2010-03-12', '2011-03-14', '2012-03-12', '2013-03-12',
               '2014-03-12', '2015-03-12', '2016-03-14', '2017-03-13'],
              dtype='datetime64[ns]', freq=None)

[rs2]

@chris-b1 When using either DateOffset or freq, is there a way to pass offset as a literal, e.g. '1Y' or '2W' and still get '2016-03-14' when using '1Y'?

[chris-b1]

@rs2 - no, that is currently not supported some discussion about that in #11375