BUG: tslib.tz_convert_single converts DST incorrectly

[sinhrks]

Apply tz_convert_single to the same time representation with different tz should be all True?

import pandas as pd
import numpy as np
import datetime
import pytz

for i in range(9):
    utc_dt = datetime.datetime(2014, 3, 9, i, 0, tzinfo=pytz.timezone('UTC'))
    tz_dt = datetime.datetime(2014, 3, 9, i, 0, tzinfo=pytz.timezone('US/Eastern'))

    utc_ts = pd.Timestamp(utc_dt)
    tz_ts = pd.Timestamp(tz_dt)

    print(utc_ts, tz_ts)

    print(utc_ts.value == pd.tslib.tz_convert_single(tz_ts.value, pytz.timezone('UTC'),
          pytz.timezone('US/Eastern')))

    print(tz_ts.value == pd.tslib.tz_convert_single(utc_ts.value, pytz.timezone('US/Eastern'),
          pytz.timezone('UTC')))

Current Result

(Timestamp('2014-03-09 00:00:00+0000', tz='UTC'), Timestamp('2014-03-09 00:00:00-0500', tz='US/Eastern'))
True
True
(Timestamp('2014-03-09 01:00:00+0000', tz='UTC'), Timestamp('2014-03-09 01:00:00-0500', tz='US/Eastern'))
True
True
(Timestamp('2014-03-09 02:00:00+0000', tz='UTC'), Timestamp('2014-03-09 02:00:00-0500', tz='US/Eastern'))
True
True
(Timestamp('2014-03-09 03:00:00+0000', tz='UTC'), Timestamp('2014-03-09 03:00:00-0500', tz='US/Eastern'))
False
True
(Timestamp('2014-03-09 04:00:00+0000', tz='UTC'), Timestamp('2014-03-09 04:00:00-0500', tz='US/Eastern'))
False
True
(Timestamp('2014-03-09 05:00:00+0000', tz='UTC'), Timestamp('2014-03-09 05:00:00-0500', tz='US/Eastern'))
False
True
(Timestamp('2014-03-09 06:00:00+0000', tz='UTC'), Timestamp('2014-03-09 06:00:00-0500', tz='US/Eastern'))
False
True
(Timestamp('2014-03-09 07:00:00+0000', tz='UTC'), Timestamp('2014-03-09 07:00:00-0500', tz='US/Eastern'))
False
True
(Timestamp('2014-03-09 08:00:00+0000', tz='UTC'), Timestamp('2014-03-09 08:00:00-0500', tz='US/Eastern'))
False
False

[rockg]

Something isn't working right in the example. The tz offset should be 0400 once dst is active and 3/9 2:00 doesn't exist. The tz_ts/tz_dt aren't right.

[jreback]

Yeah the creation is off, you have to localize with the zone localizer

In [10]: pytz.timezone('US/Eastern').localize(datetime.datetime(2014,3,9,2))
Out[10]: datetime.datetime(2014, 3, 9, 2, 0, tzinfo=<DstTzInfo 'US/Eastern' EST-1 day, 19:00:00 STD>)

In [11]: pytz.timezone('US/Eastern').localize(datetime.datetime(2014,3,9,3))
Out[11]: datetime.datetime(2014, 3, 9, 3, 0, tzinfo=<DstTzInfo 'US/Eastern' EDT-1 day, 20:00:00 DST>)

[sinhrks]

Ah, modified example and result.

import pandas as pd
import numpy as np
import datetime
import pytz


for i in range(9):
    utc_ts = pd.Timestamp('2014-03-09 {0:02d}:00'.format(i), tz='UTC')
    tz_ts = pd.Timestamp('2014-03-09 {0:02}:00'.format(i), tz='US/Eastern')

    print(utc_ts, tz_ts)

    print(utc_ts.value == pd.tslib.tz_convert_single(tz_ts.value, pytz.timezone('UTC'),
          pytz.timezone('US/Eastern')))

    print(tz_ts.value == pd.tslib.tz_convert_single(utc_ts.value, pytz.timezone('US/Eastern'),
          pytz.timezone('UTC')))

Updated Result

(Timestamp('2014-03-09 00:00:00+0000', tz='UTC'), Timestamp('2014-03-09 00:00:00-0500', tz='US/Eastern'))
True
True
(Timestamp('2014-03-09 01:00:00+0000', tz='UTC'), Timestamp('2014-03-09 01:00:00-0500', tz='US/Eastern'))
True
True
(Timestamp('2014-03-09 02:00:00+0000', tz='UTC'), Timestamp('2014-03-09 02:00:00-0500', tz='US/Eastern'))
False
True
(Timestamp('2014-03-09 03:00:00+0000', tz='UTC'), Timestamp('2014-03-09 03:00:00-0400', tz='US/Eastern'))
True
False
(Timestamp('2014-03-09 04:00:00+0000', tz='UTC'), Timestamp('2014-03-09 04:00:00-0400', tz='US/Eastern'))
True
False
(Timestamp('2014-03-09 05:00:00+0000', tz='UTC'), Timestamp('2014-03-09 05:00:00-0400', tz='US/Eastern'))
True
False
(Timestamp('2014-03-09 06:00:00+0000', tz='UTC'), Timestamp('2014-03-09 06:00:00-0400', tz='US/Eastern'))
True
False
(Timestamp('2014-03-09 07:00:00+0000', tz='UTC'), Timestamp('2014-03-09 07:00:00-0400', tz='US/Eastern'))
True
False
(Timestamp('2014-03-09 08:00:00+0000', tz='UTC'), Timestamp('2014-03-09 08:00:00-0400', tz='US/Eastern'))
True
True

[sinhrks]

I understand UTC <-> local conversion results can differ on edges of DST because it has timestamps which is invalid. If test case added in #7798 test_tslib_tz_convert_dst looks correct, please close this.

[jreback]

@rockg can you have a look....

[jreback]

@sinhrks so this is indepent of #7798 ?

[sinhrks]

Yes, independent. (Background was considering test cases for #7798, though)

• This is asking conversion logic itself (and I understand my question was incorrect).
• BUG: tslib.tz_convert and tslib.tz_convert_single may output different result in DST #7798 fixes the edge cases of DST, using current conversion logic.

[sinhrks]

@jreback pls close this, as curretn tresults are correct.