BUG: Some date-like Offset.apply resets time

[sinhrks]

There seems to be inconsistencies regarding time (hours, minutes, etc) handling of Offset.apply. Maybe all these should preserve hours/minutes like DayOffset? Or any other rules?

Followings are results offset(n=1) applied to datetime(2011, 1, 1, 9, 0).

# Offsets which preserves time
(<Day>, datetime.datetime(2011, 1, 2, 9, 0))
(<BusinessDay>, Timestamp('2011-01-03 09:00:00'))
(<CustomBusinessDay>, Timestamp('2011-01-03 09:00:00'))
(<MonthBegin>, Timestamp('2011-02-01 09:00:00'))
(<CustomBusinessMonthBegin>, Timestamp('2011-01-03 09:00:00'))
(<YearBegin: month=1>, Timestamp('2012-01-01 09:00:00'))
(<YearEnd: month=12>, Timestamp('2011-12-31 09:00:00'))
(<BusinessYearEnd: month=12>, Timestamp('2011-12-30 09:00:00'))
(<QuarterBegin: startingMonth=3>, Timestamp('2011-03-01 09:00:00'))
(<BusinessQuarterBegin: startingMonth=3>, Timestamp('2011-03-01 09:00:00'))
(<QuarterEnd: startingMonth=3>, Timestamp('2011-03-31 09:00:00'))
(<BusinessQuarterEnd: startingMonth=3>, Timestamp('2011-03-31 09:00:00'))
(<Week: weekday=None>, Timestamp('2011-01-08 09:00:00'))

# Offsets which don't preserves time
(<BusinessMonthBegin>, Timestamp('2011-01-03 00:00:00'))
(<MonthEnd>, Timestamp('2011-01-31 00:00:00'))
(<BusinessMonthEnd>, Timestamp('2011-01-31 00:00:00'))
(<CustomBusinessMonthEnd>, Timestamp('2011-01-31 00:00:00'))
(<BusinessYearBegin: month=1>, Timestamp('2011-01-03 00:00:00'))
(<LastWeekOfMonth: weekday=5>, Timestamp('2011-01-29 00:00:00'))
(<FY5253Quarter: kwds={'startingMonth': 1, 'weekday': 1, 'variation': 'last'}, qtr_with_extra_week=1>, Timestamp('2011-01-25 00:00:00'))
(<FY5253: kwds={'qtr_with_extra_week': 1}, startingMonth=1, variation='last', weekday=1>, Timestamp('2011-01-25 00:00:00'))
(<LastWeekOfMonth: weekday=5>, Timestamp('2011-01-29 00:00:00'))
(<Easter>, datetime.datetime(2011, 4, 24, 0, 0))

[jreback]

hmm afaik these should all preserve times

I think the time preservation may not be handled properly in apply

prob no tests for this either

feel free to add tests / fix

[sinhrks]

Thanks. I found BusinessDay, CustomBusinessDay, CustomBusinessMonthEnd and CustomBusinessMonthBegin already have normalize option to normalize the date. How about adding normalize option to all the offset with default False?

The option should affect to apply, rollforward, rollback and onOffset.

import pandas as pd
pd.offsets.Day().apply(pd.Timestamp('2011-01-01 09:00:00'))
# 2011-01-02 09:00:00

pd.offsets.Day(normalize=True).apply(pd.Timestamp('2011-01-01 09:00:00'))
# 2011-01-02 00:00:00

pd.offsets.Day().rollforward(pd.Timestamp('2011-01-01 09:00:00'))
# 2011-01-01 09:00:00

pd.offsets.Day(normalize=True).rollforward(pd.Timestamp('2011-01-01 09:00:00'))
# 2011-01-02 00:00:00

pd.offsets.Day().onOffset(pd.Timestamp('2011-01-01 09:00:00'))
# True

pd.offsets.Day(normalize=True).rollforward(pd.Timestamp('2011-01-01 09:00:00'))
# False

pd.offsets.Day(normalize=True).rollforward(pd.Timestamp('2011-01-02 00:00:00'))
# True

[jreback]

yes I think all offsets should handle normalize (default of False)
refactor out to a function

and tests for all offsets (which is the best way to ensure that they have consistent functionality)
eg out automated tests for all offsets in Base (which we have for other things, eg making sure apply returns a Timestamp for example)