display-time-world & EDT/DST

display-time-world & EDT/DST

[Jambunathan K]

,---- M-x display-time-world
| Seattle   Wednesday 27 June 01:24 PDT
| New York  Wednesday 27 June 04:24 EDT <===  Off by 1 hr 
| London    Wednesday 27 June 09:24 BST
| Paris     Wednesday 27 June 10:24 CDT
| Bangalore Wednesday 27 June 14:54 IST <=== Local Timezone
| Tokyo     Wednesday 27 June 18:24 JST
`----

,---- http://www.timeanddate.com/worldclock/city.html?n=179
| 
| Current Time|Wednesday, 27 June 2012, 05:27:42 EDT <=== Time now
| 
| | Standard time zone:       | UTC/GMT -5 hours            |
| | Daylight saving time:     | +1 hour                     |
| | Current time zone offset: | UTC/GMT -4 hours            |
| | Time zone abbreviation:   | EDT - Eastern Daylight Time |
`----

As you can see, the time reported by Emacs is off by 1 hr.  Is there a
way to fix it?

Also I could take some help with interpreting the value of this
variable.  Should display-time-world be documented in Emacs reference
manual? 

,----[ C-h v display-time-world-list RET ]
| display-time-world-list is a variable defined in `time.el'.
| Its value is (("PST8PDT" "Seattle")
|  ("EST5EDT" "New York")
|  ("GMT0BST" "London")
|  ("CET-1CDT" "Paris")
|  ("IST-5:30" "Bangalore")  <=== Why this ''minus''. Isn't IST = GMT+5:30?
|  ("JST-9" "Tokyo"))
| 
| 
| Documentation:
| Alist of time zones and places for `display-time-world' to display.
| Each element has the form (TIMEZONE LABEL).
| TIMEZONE should be in a format supported by your system.  See the
| documentation of `zoneinfo-style-world-list' and
| `legacy-style-world-list' for two widely used formats.  LABEL is
| a string to display as the label of that TIMEZONE's time.
| 
| You can customize this variable.
| 
| This variable was introduced, or its default value was changed, in
| version 23.1 of Emacs.
| 
| [back]
`----



ps: I am really interested in local Ottawa time (which is apparently
same as NY's throughout the year)

-- 

Re: display-time-world & EDT/DST

[John Wiegley]

>>>>> Jambunathan K <kjambunathan@gmail.com> writes:

> ,---- http://www.timeanddate.com/worldclock/city.html?n=179| 
> | Current Time|Wednesday, 27 June 2012, 05:27:42 EDT <=== Time now
> | 
> | | Standard time zone:       | UTC/GMT -5 hours            |
> | | Daylight saving time:     | +1 hour                     |
> | | Current time zone offset: | UTC/GMT -4 hours            |
> | | Time zone abbreviation:   | EDT - Eastern Daylight Time |
> `----

> As you can see, the time reported by Emacs is off by 1 hr.  Is there a way
> to fix it?

Thanks for reporting this, would you mind filing a bug with M-x emacs-bug?

John

Re: display-time-world & EDT/DST

[Jason Rumney]

On Wednesday, 27 June 2012 17:39:05 UTC+8, Jambunathan K  wrote:
 
> ,----[ C-h v display-time-world-list RET ]
> | display-time-world-list is a variable defined in `time.el'.
> | Its value is (("PST8PDT" "Seattle")
> |  ("EST5EDT" "New York")
> |  ("GMT0BST" "London")
> |  ("CET-1CDT" "Paris")
> |  ("IST-5:30" "Bangalore")  <=== Why this ''minus''. Isn't IST = GMT+5:30?
> |  ("JST-9" "Tokyo"))
> | 

The history of the development of computer software is largely a US one. When the TZ offset format was defined, US timezones were defined as positive. So we ended up with a backwards system, where the TZ offset is actually specifying how many hours you need to SUBTRACT from UTC to get local time.