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pytz question: GMT vs. UTC

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  pytz question: GMT vs. UTC Skip Montanaro <skip@pobox.com> - 2014-01-29 11:29 -0600
    Re: pytz question: GMT vs. UTC Grant Edwards <invalid@invalid.invalid> - 2014-01-29 19:02 +0000
      Re: pytz question: GMT vs. UTC Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-01-29 19:17 -0500
      Re: pytz question: GMT vs. UTC Chris Angelico <rosuav@gmail.com> - 2014-01-30 11:28 +1100
      Re: pytz question: GMT vs. UTC Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-01-29 20:50 -0500
      Re: pytz question: GMT vs. UTC MRAB <python@mrabarnett.plus.com> - 2014-01-30 02:40 +0000
      Re: pytz question: GMT vs. UTC Chris Angelico <rosuav@gmail.com> - 2014-01-30 14:27 +1100
        Re: pytz question: GMT vs. UTC wxjmfauth@gmail.com - 2014-01-30 00:45 -0800
          Re: pytz question: GMT vs. UTC MRAB <python@mrabarnett.plus.com> - 2014-01-30 11:51 +0000
          Re: pytz question: GMT vs. UTC Grant Edwards <invalid@invalid.invalid> - 2014-01-30 15:21 +0000
            Re: pytz question: GMT vs. UTC Dan Sommers <dan@tombstonezero.net> - 2014-01-31 04:08 +0000
              Re: pytz question: GMT vs. UTC Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-01-31 04:37 +0000
                Re: pytz question: GMT vs. UTC Dan Sommers <dan@tombstonezero.net> - 2014-01-31 06:28 +0000
                  Re: pytz question: GMT vs. UTC Chris Angelico <rosuav@gmail.com> - 2014-01-31 17:42 +1100
                    Re: pytz question: GMT vs. UTC Dan Sommers <dan@tombstonezero.net> - 2014-02-01 06:30 +0000
                Re: pytz question: GMT vs. UTC Roy Smith <roy@panix.com> - 2014-01-31 10:00 -0500
              Re: pytz question: GMT vs. UTC Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-01-31 09:59 +0000
            Re: pytz question: GMT vs. UTC Pete Forman <petef4+usenet@gmail.com> - 2014-02-02 12:45 +0000
              Re: pytz question: GMT vs. UTC wxjmfauth@gmail.com - 2014-02-02 06:38 -0800
              Re: pytz question: GMT vs. UTC Grant Edwards <invalid@invalid.invalid> - 2014-02-02 16:03 +0000
          Re: pytz question: GMT vs. UTC Rustom Mody <rustompmody@gmail.com> - 2014-01-30 23:02 -0800
            Re: pytz question: GMT vs. UTC wxjmfauth@gmail.com - 2014-01-31 02:17 -0800
              Re: pytz question: GMT vs. UTC Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-01-31 14:50 +0000
                Re: pytz question: GMT vs. UTC Roy Smith <roy@panix.com> - 2014-01-31 10:04 -0500
                  Re: pytz question: GMT vs. UTC Robert Kern <robert.kern@gmail.com> - 2014-01-31 15:08 +0000
      Re: pytz question: GMT vs. UTC Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-01-30 19:44 +1300
      Re: pytz question: GMT vs. UTC Christian Heimes <christian@python.org> - 2014-01-30 10:49 +0100
        Re: pytz question: GMT vs. UTC wxjmfauth@gmail.com - 2014-01-30 02:10 -0800
        Re: pytz question: GMT vs. UTC Grant Edwards <invalid@invalid.invalid> - 2014-01-30 15:23 +0000
          Re: pytz question: GMT vs. UTC Larry Martell <larry.martell@gmail.com> - 2014-01-30 10:28 -0500
      Re: pytz question: GMT vs. UTC Chris Angelico <rosuav@gmail.com> - 2014-01-30 21:10 +1100
      Re: pytz question: GMT vs. UTC Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-01-30 20:18 -0500

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#64944 — pytz question: GMT vs. UTC

According ato the pytz doc (http://pytz.sourceforge.net/):

"‘UTC’ is Universal Time, also known as Greenwich Mean Time or GMT in
the United Kingdom."

If they are equal, why don't timezone objects created from those two
strings compare equal?

>>> pytz.timezone("UTC") == pytz.timezone("GMT")
False

(I'm revealing my complete ignorance of timezone manipulation by
asking this question.)

Thx,

Skip

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#64948

On 2014-01-29, Skip Montanaro <skip@pobox.com> wrote:
> According ato the pytz doc (http://pytz.sourceforge.net/):
>
> "UTC is Universal Time, also known as Greenwich Mean Time or GMT in
> the United Kingdom."
>
> If they are equal,

The question is _are_ they equal?

There is an exact defintion for what "UTC" is, and there's another
exact definition of what UT1 is (more about this later).  Civil
timezones are defined as offsets from UTC.

It seems that "GMT" no longer has an exact definition (at least from a
metrologist's perspective) can be used to mean either UTC or UT1.  UTC
and UT1 can differ by up to 1 second.  Leap seconds are occasionally
added to UTC to keep it from drifting more than 1 second from UT1. 

From a metrology point of view, what was originally called "GMT"
(solar time at 0 degrees longtitude) is now called "UT1".  So some
people rightly claim that "GMT" means UT1. But nobody actually _uses_
UT1 (except metrologists and astronomers).

All civil time is based on UTC: the official time in Greenwich (except
during BST) is not UT1, it's UTC.  So some other people rightly claim
that "GMT" refers to UTC.

In a software libary context, I would say that GMT should mean UTC and
they ought to be considered equal and should always produce identical
results.  In a metrology context, people saying "GMT" probably ought
to be smacked across the knuckes with a 12-inch platinum-iridium ruler
and asked to try again until they specify either UTC or UT1 (or some
other precisely defined UT-flavor).

http://en.wikipedia.org/wiki/Universal_Time

-- 
Grant Edwards               grant.b.edwards        Yow! A dwarf is passing out
                                  at               somewhere in Detroit!
                              gmail.com            

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#64957

On Wed, 29 Jan 2014 19:02:53 +0000 (UTC), Grant Edwards
<invalid@invalid.invalid> declaimed the following:


>to be smacked across the knuckes with a 12-inch platinum-iridium ruler

	Under what temperature/pressure conditions is that ruler?
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#64958

On Thu, Jan 30, 2014 at 11:17 AM, Dennis Lee Bieber
<wlfraed@ix.netcom.com> wrote:
> On Wed, 29 Jan 2014 19:02:53 +0000 (UTC), Grant Edwards
> <invalid@invalid.invalid> declaimed the following:
>
>
>>to be smacked across the knuckes with a 12-inch platinum-iridium ruler
>
>         Under what temperature/pressure conditions is that ruler?

STP, of course. And the smack must be administered in exactly 1G
environment, to ensure proper impact.

ChrisA

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#64960

On Thu, 30 Jan 2014 11:28:16 +1100, Chris Angelico <rosuav@gmail.com>
declaimed the following:

>On Thu, Jan 30, 2014 at 11:17 AM, Dennis Lee Bieber
><wlfraed@ix.netcom.com> wrote:
>> On Wed, 29 Jan 2014 19:02:53 +0000 (UTC), Grant Edwards
>> <invalid@invalid.invalid> declaimed the following:
>>
>>
>>>to be smacked across the knuckes with a 12-inch platinum-iridium ruler
>>
>>         Under what temperature/pressure conditions is that ruler?
>
>STP, of course. And the smack must be administered in exactly 1G
>environment, to ensure proper impact.
>
	How cruel... I suspect the smack at 0degC is much more painful than one
at room temperature <G>
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#64961

On 2014-01-30 01:50, Dennis Lee Bieber wrote:
> On Thu, 30 Jan 2014 11:28:16 +1100, Chris Angelico <rosuav@gmail.com>
> declaimed the following:
>
>>On Thu, Jan 30, 2014 at 11:17 AM, Dennis Lee Bieber
>><wlfraed@ix.netcom.com> wrote:
>>> On Wed, 29 Jan 2014 19:02:53 +0000 (UTC), Grant Edwards
>>> <invalid@invalid.invalid> declaimed the following:
>>>
>>>
>>>>to be smacked across the knuckes with a 12-inch platinum-iridium ruler
>>>
>>>         Under what temperature/pressure conditions is that ruler?
>>
>>STP, of course. And the smack must be administered in exactly 1G
>>environment, to ensure proper impact.
>>
> 	How cruel... I suspect the smack at 0degC is much more painful than one
> at room temperature <G>
>
It's the 21st century; you should be making use of Unicode: 0°C.

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#64962

On Thu, Jan 30, 2014 at 1:40 PM, MRAB <python@mrabarnett.plus.com> wrote:
>>         How cruel... I suspect the smack at 0degC is much more painful
>> than one
>> at room temperature <G>
>>
> It's the 21st century; you should be making use of Unicode: 0°C.

I started to read that and thought you were going to advocate the use of 0°K...

ChrisA

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#64972

Le jeudi 30 janvier 2014 04:27:54 UTC+1, Chris Angelico a écrit :
> On Thu, Jan 30, 2014 at 1:40 PM, MRAB <python@mrabarnett.plus.com> wrote:
> 
> >>         How cruel... I suspect the smack at 0degC is much more painful
> 
> >> than one
> 
> >> at room temperature <G>
> 
> >>
> 
> > It's the 21st century; you should be making use of Unicode: 0°C.
> 
> 
> 
> I started to read that and thought you were going to advocate the use of 0°K...
> 
> 

======

The temperature unit is the "Kelvin", not the "Degree Kelvin".
One writes: 0 K, 275.15 K

It can also be the "Degree Celsius", not the "Celsius".
One writes: -273.15 °C, 0 °C



>>> import unicodedata as ud
>>> for c in '\u2109\u212a\u2103\u00b0':
...     print(ud.name(c))
...     
DEGREE FAHRENHEIT
KELVIN SIGN
DEGREE CELSIUS
DEGREE SIGN
>>>

jmf

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#64984

On 2014-01-30 08:45, wxjmfauth@gmail.com wrote:
> Le jeudi 30 janvier 2014 04:27:54 UTC+1, Chris Angelico a écrit :
>> On Thu, Jan 30, 2014 at 1:40 PM, MRAB <python@mrabarnett.plus.com> wrote:
>>
>> >>         How cruel... I suspect the smack at 0degC is much more painful
>>
>> >> than one
>>
>> >> at room temperature <G>
>>
>> >>
>>
>> > It's the 21st century; you should be making use of Unicode: 0°C.
>>
>>
>>
>> I started to read that and thought you were going to advocate the use of 0°K...
>>
>>
>
> ======
>
> The temperature unit is the "Kelvin", not the "Degree Kelvin".
> One writes: 0 K, 275.15 K
>
Not that long ago I saw a science fiction film in which one of the
"scientists" said "degrees Kelvin". The rest of the "science" was
somewhat dubious too...

> It can also be the "Degree Celsius", not the "Celsius".
> One writes: -273.15 °C, 0 °C
>
>
>
>>>> import unicodedata as ud
>>>> for c in '\u2109\u212a\u2103\u00b0':
> ...     print(ud.name(c))
> ...
> DEGREE FAHRENHEIT
> KELVIN SIGN
> DEGREE CELSIUS
> DEGREE SIGN
>>>>
>

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#65020

On 2014-01-30, wxjmfauth@gmail.com <wxjmfauth@gmail.com> wrote:

> The temperature unit is the "Kelvin", not the "Degree Kelvin".
> One writes: 0 K, 275.15 K

And remember to say "Kelvins" not "Kelvin" when speaking about
temperatures other than 1 K.

-- 
Grant Edwards               grant.b.edwards        Yow! BELA LUGOSI is my
                                  at               co-pilot ...
                              gmail.com            

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#65084

On Thu, 30 Jan 2014 15:21:35 +0000, Grant Edwards wrote:

> On 2014-01-30, wxjmfauth@gmail.com <wxjmfauth@gmail.com> wrote:
> 
>> The temperature unit is the "Kelvin", not the "Degree Kelvin".
>> One writes: 0 K, 275.15 K
> 
> And remember to say "Kelvins" not "Kelvin" when speaking about
> temperatures other than 1 K.

And -1 K.¹  *wink*

¹ http://meta.stackoverflow.com/questions/165244/is-negative-one-plural
  notwithstanding

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#65086

On Fri, 31 Jan 2014 04:08:46 +0000, Dan Sommers wrote about temperatures:

> And -1 K.


You josh, but there are negative temperatures in Kelvin. They're hotter 
than infinitely hot.

http://en.wikipedia.org/wiki/Negative_temperature


-- 
Steven

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#65098

On Fri, 31 Jan 2014 04:37:16 +0000, Steven D'Aprano wrote:

> On Fri, 31 Jan 2014 04:08:46 +0000, Dan Sommers wrote about temperatures:
> 
>> And -1 K.
> 
> You josh, but there are negative temperatures in Kelvin. They're hotter 
> than infinitely hot.
> 
> http://en.wikipedia.org/wiki/Negative_temperature

That's what I get for stopping with an undergraduate degree in physics.

Thanks for the link; I learned something interesting today.

ObPython:  My program retrieves temperatures (in Kelvins) from an
external device (the details of which I am not at liberty to discuss)
and stores them in the cloud (because that's where all the cool kids
store data these days), and there's something really weird going on.

Here's my code and the output, filtered through http://sscce.org/:

    $ cat ./program.py

    import cloudstorageinterface

    temperature1 = cloudstorageinterface.get_a_temperature()
    temperature2 = cloudstorageinterface.get_a_temperature()

    print('temperature1 is', temperature1, 'K')
    print('temperature2 is', temperature2, 'K')

    if temperature2 > temperature1:
	print('temperature2 is hotter than temperature1')

    if temperature2 < temperature1:
	print('temperature1 is hotter than temperature2')

    if temperature2 == temperature1:
	print("this can't happen")

    $ python ./program.py
    temperature1 is -100 K
    temperature2 is 100 K
    temperature2 is hotter than temperature1

But everyone knows that -100K is hotter than 100K.  I tried converting
to UTC, but that didn't help.  What am I missing?

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#65100

On Fri, Jan 31, 2014 at 5:28 PM, Dan Sommers <dan@tombstonezero.net> wrote:
> ObPython:  My program retrieves temperatures (in Kelvins) from an
> external device (the details of which I am not at liberty to discuss)
> and stores them in the cloud (because that's where all the cool kids
> store data these days), and there's something really weird going on.
>
>
>     $ python ./program.py
>     temperature1 is -100 K
>     temperature2 is 100 K
>     temperature2 is hotter than temperature1
>
> But everyone knows that -100K is hotter than 100K.  I tried converting
> to UTC, but that didn't help.  What am I missing?

I'm sorry, you have completely misunderstood the problem here. You are
storing data in the cloud, which means you're representing everything
with water. It is therefore fundamentally illogical to use any
temperature outside the range [273.15K, 373.15K], because otherwise
your cloud will freeze or boil, and either way, it'll crash badly.

Plus, converting to UTC? Puh-leeze. You should be using kilogram
meters per second.

ChrisA

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#65202

On Fri, 31 Jan 2014 17:42:30 +1100, Chris Angelico wrote:

> On Fri, Jan 31, 2014 at 5:28 PM, Dan Sommers <dan@tombstonezero.net> wrote:
>> ObPython:  My program retrieves temperatures (in Kelvins) from an
>> external device (the details of which I am not at liberty to discuss)
>> and stores them in the cloud (because that's where all the cool kids
>> store data these days), and there's something really weird going on.
>>
>>     $ python ./program.py
>>     temperature1 is -100 K
>>     temperature2 is 100 K
>>     temperature2 is hotter than temperature1
>>
>> But everyone knows that -100K is hotter than 100K.  I tried converting
>> to UTC, but that didn't help.  What am I missing?
> 
> I'm sorry, you have completely misunderstood the problem here. You are
> storing data in the cloud, which means you're representing everything
> with water. It is therefore fundamentally illogical to use any
> temperature outside the range [273.15K, 373.15K], because otherwise
> your cloud will freeze or boil, and either way, it'll crash badly.

I think I found the problem:  it's not a water cloud, it's a potassium
sulfide cloud, and as its temperatures rose, I lost the special Ks.

> Plus, converting to UTC? Puh-leeze. You should be using kilogram
> meters per second.

It was a momentary lapse of reason.  Sorry.

Dan

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#65124

In article <52eb287c$0$29972$c3e8da3$5496439d@news.astraweb.com>,
 Steven D'Aprano <steve+comp.lang.python@pearwood.info> wrote:

> On Fri, 31 Jan 2014 04:08:46 +0000, Dan Sommers wrote about temperatures:
> 
> > And -1 K.
> 
> 
> You josh, but there are negative temperatures in Kelvin. They're hotter 
> than infinitely hot.
> 
> http://en.wikipedia.org/wiki/Negative_temperature

Negative Kelvins also have meaning as relative measurements.  "The 
framzit is changing temperature at a rate of -3.6 K per gigafortnight"

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#65107

On 31/01/2014 04:08, Dan Sommers wrote:
> On Thu, 30 Jan 2014 15:21:35 +0000, Grant Edwards wrote:
>
>> On 2014-01-30, wxjmfauth@gmail.com <wxjmfauth@gmail.com> wrote:
>>
>>> The temperature unit is the "Kelvin", not the "Degree Kelvin".
>>> One writes: 0 K, 275.15 K
>>
>> And remember to say "Kelvins" not "Kelvin" when speaking about
>> temperatures other than 1 K.
>
> And -1 K.¹  *wink*
>
> ¹ http://meta.stackoverflow.com/questions/165244/is-negative-one-plural
>    notwithstanding
>

Does that -1 allow for the wind chill factor or not?

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence

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#65260

Grant Edwards <invalid@invalid.invalid> writes:

> On 2014-01-30, wxjmfauth@gmail.com <wxjmfauth@gmail.com> wrote:
>
>> The temperature unit is the "Kelvin", not the "Degree Kelvin".
>> One writes: 0 K, 275.15 K
>
> And remember to say "Kelvins" not "Kelvin" when speaking about
> temperatures other than 1 K.

And remember to write kelvins. SI units named after people such as
kelvin, watt and pascal are lower case while their symbols have a
leading capital: K, W, Pa.
-- 
Pete Forman

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#65263

Le dimanche 2 février 2014 13:45:54 UTC+1, Pete Forman a écrit :
> Grant Edwards <invalid@invalid.invalid> writes:
> 
> 
> 
> > On 2014-01-30, wxjmfauth@gmail.com <wxjmfauth@gmail.com> wrote:
> 
> >
> 
> >> The temperature unit is the "Kelvin", not the "Degree Kelvin".
> 
> >> One writes: 0 K, 275.15 K
> 
> >
> 
> > And remember to say "Kelvins" not "Kelvin" when speaking about
> 
> > temperatures other than 1 K.
> 
> 
> 
> And remember to write kelvins. SI units named after people such as
> 
> kelvin, watt and pascal are lower case while their symbols have a
> 
> leading capital: K, W, Pa.
> 
> -- 
> 
> Pete Forman

Yes, correct.

(I focussed on the word *degree* in the expression
"degree kelvin".

jmf

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#65266

On 2014-02-02, Pete Forman <petef4+usenet@gmail.com> wrote:
> Grant Edwards <invalid@invalid.invalid> writes:
>
>> On 2014-01-30, wxjmfauth@gmail.com <wxjmfauth@gmail.com> wrote:
>>
>>> The temperature unit is the "Kelvin", not the "Degree Kelvin".
>>> One writes: 0 K, 275.15 K
>>
>> And remember to say "Kelvins" not "Kelvin" when speaking about
>> temperatures other than 1 K.
>
> And remember to write kelvins. SI units named after people such as
> kelvin, watt and pascal are lower case while their symbols have a
> leading capital: K, W, Pa.

Indeed. Many years ago, I was taught to capitalize units that were
originally proper nouns.  I'm pretty sure this isn't the first time
I've learned that is incorrect, but my fingers keep insisting on doing
it.  Interestingly, one does capitalizes Celsius when writing "degrees
Celsius" [at least according to the NIST].

http://physics.nist.gov/Pubs/SP811/sec09.html

-- 
Grant

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