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Re: Matplotlib X-axis timezone trouble [SOLVED]

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On Sat, 04 Jul 2015 07:29:45 +0300, Akira Li <4kir4.1i@gmail.com> wrote:
> Peter Pearson <pkpearson@nowhere.invalid> writes:
>
>> The following code produces a plot with a line running from (9:30, 0) to
>> (10:30, 1), not from (8:30, 0) to (9:30, 1) as I desire.
>>
>> If I use timezone None instead of pacific, the plot is as desired, but
>> of course that doesn't solve the general problem of which this is a
>> much-reduced example.
>>
>> If I use timezone US/Central, I get the same (bad) plot.
>>
>> import matplotlib.pyplot as plt
>> import datetime
>> import pytz
>> pacific = pytz.timezone("US/Pacific")
>> fig = plt.figure()
>> plt.plot([datetime.datetime(2014, 10, 7, 8, 30, tzinfo=pacific),
>>           datetime.datetime(2014, 10, 7, 9, 30, tzinfo=pacific)],
>>          [0,1], marker="o", color="green")
>> fig.autofmt_xdate()
>> plt.show()
>>
>> Does anybody know why this shift is occurring?  Is Matplotlib
>> confused about what timezone to use in labeling the axis?  How
>> would I tell it what timezone to use (preferably explicitly in
>> the code, not in matplotlibrc)?
>>
>
> Your pytz usage is incorrect.
>
> Don't pass a pytz tzinfo object to the datetime construtor directly, use
> `.localize()` method instead. Read the note at the very beginning of
> pytz docs http://pytz.sourceforge.net/

Exactly.  Thank you.

For newcomers, the denouement of this thread is this:

 * Matplotlib had nothing to do with this problem, it was correctly
   displaying bad datetime.datetime values.

 * Python's datetime.datetime(..., tzinfo=timezone) is unreliable if
   timezone has daylight-saving time.

 * pytz's creators provide the localize() method specifically to
   remedy this problem.  If you want to create a datetime object
   that has a timezone that might have daylight-saving time,
   use localize().

-- 
To email me, substitute nowhere->runbox, invalid->com.

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Thread

Matplotlib X-axis timezone trouble Peter Pearson <pkpearson@nowhere.invalid> - 2015-06-30 00:56 +0000
  Re: Matplotlib X-axis timezone trouble Laura Creighton <lac@openend.se> - 2015-06-30 04:03 +0200
    Re: Matplotlib X-axis timezone trouble Peter Pearson <pkpearson@nowhere.invalid> - 2015-06-30 04:57 +0000
  Re: Matplotlib X-axis timezone trouble Chris Angelico <rosuav@gmail.com> - 2015-06-30 12:11 +1000
    Re: Matplotlib X-axis timezone trouble Peter Pearson <pkpearson@nowhere.invalid> - 2015-06-30 04:49 +0000
      Re: Matplotlib X-axis timezone trouble Chris Angelico <rosuav@gmail.com> - 2015-06-30 17:01 +1000
        Re: Matplotlib X-axis timezone trouble Peter Pearson <pkpearson@nowhere.invalid> - 2015-06-30 16:42 +0000
          Re: Matplotlib X-axis timezone trouble Chris Angelico <rosuav@gmail.com> - 2015-07-01 02:55 +1000
  Re: Matplotlib X-axis timezone trouble Peter Pearson <pkpearson@nowhere.invalid> - 2015-07-01 05:50 +0000
    Re: Matplotlib X-axis timezone trouble Chris Angelico <rosuav@gmail.com> - 2015-07-01 17:15 +1000
      Datetime timezone trouble (was: Matplotlib X-axis timezone trouble) Peter Pearson <pkpearson@nowhere.invalid> - 2015-07-01 16:36 +0000
        Re: Datetime timezone trouble (was: Matplotlib X-axis timezone trouble) Ian Kelly <ian.g.kelly@gmail.com> - 2015-07-01 10:55 -0600
          Re: Datetime timezone trouble (was: Matplotlib X-axis timezone trouble) Peter Pearson <pkpearson@nowhere.invalid> - 2015-07-01 19:09 +0000
        Re: Datetime timezone trouble (was: Matplotlib X-axis timezone trouble) Chris Angelico <rosuav@gmail.com> - 2015-07-02 03:08 +1000
  Re: Matplotlib X-axis timezone trouble Akira Li <4kir4.1i@gmail.com> - 2015-07-04 07:29 +0300
    Re: Matplotlib X-axis timezone trouble [SOLVED] Peter Pearson <pkpearson@nowhere.invalid> - 2015-07-04 17:37 +0000
  Re: Matplotlib X-axis timezone trouble Tony the Tiger <tony@tiger.invalid> - 2015-07-09 19:50 +0000
    Re: Matplotlib X-axis timezone trouble Peter Pearson <pkpearson@nowhere.invalid> - 2015-07-10 16:15 +0000

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