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BUG: Easter works incorrectly in negative offsets #7195

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Merged
merged 1 commit into from
Jun 3, 2014
Merged

BUG: Easter works incorrectly in negative offsets #7195

merged 1 commit into from
Jun 3, 2014
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sinhrks
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@sinhrks sinhrks commented May 21, 2014

When an offset is negative, Easter skips the date just before and returns one before.

(- pd.offsets.Easter()).apply(pd.Timestamp('2011-01-01 09:00:00'))
#2009-04-12 00:00:00

(- pd.offsets.Easter()).apply(pd.Timestamp('2012-01-01 09:00:00'))
# returns 2010-04-04 00:00:00

(- pd.offsets.Easter()).apply(pd.Timestamp('2010-04-05 09:00:00'))
#2009-04-12 00:00:00

@jreback jreback added this to the 0.14.1 milestone May 21, 2014
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jreback commented May 21, 2014

this just Easter or a more general holiday apply issue?

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sinhrks commented May 24, 2014

Other offset looks handle negative offsets correctly. I'll check other offsets during #7156.

jreback added a commit that referenced this pull request Jun 3, 2014
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Merge pull request #7195 from sinhrks/easter
97ad707 
BUG: Easter works incorrectly in negative offsets
@jreback jreback merged commit 97ad707 into pandas-dev:master Jun 3, 2014
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jreback commented Jun 3, 2014

thanks

@sinhrks sinhrks deleted the easter branch June 5, 2014 12:44
jbrockmendel
jbrockmendel reviewed Dec 19, 2017
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pandas/tseries/offsets.py
new = easter(other.year + self.n)
elif other < currentEaster:
new = easter(other.year + self.n - 1)
if self.n >= 0:
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@sinhrks This checks self.n >= 0 while pretty much all other offsets check self.n > 0. Is this difference intentional? If so I'd like to add a brief comment explaining why.

Up-to-date location for this check:
https://github.com/pandas-dev/pandas/blob/master/pandas/tseries/offsets.py#L2129

Examples for other offset classes:
https://github.com/pandas-dev/pandas/blob/master/pandas/tseries/offsets.py#L950
https://github.com/pandas-dev/pandas/blob/master/pandas/tseries/offsets.py#L1409
https://github.com/pandas-dev/pandas/blob/master/pandas/tseries/offsets.py#L1572
https://github.com/pandas-dev/pandas/blob/master/pandas/tseries/offsets.py#L1053

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