Format modifier suggestion for format-time-string

Format modifier suggestion for format-time-string

[Edward O'Connor]

Hi.

When generating data formats that rely on RFC 3339 date and time formats
(Atom, say) in elisp, I've often found myself having to do something
like this:

(defun rfc3339-datetime (&optional time)
  (let ((stamp (format-time-string "%Y-%m-%dT%H:%M:%S%z" time)))
    (format "%s:%s" (substring stamp 0 -2) (substring stamp -2))))

In RFC 3339, the colon separating hours and minutes within a time zone
offset is mandatory, but `format-time-string' doesn't have the ability
to generate time zone offsets with a colon in them.

I'd like to suggest the addition of a : modifier, such that
(format-time-string "%:z") would generate an RFC 3339-compatible time
zone offset.

What do you think?


Thanks for the consideration,
Ted

Re: Format modifier suggestion for format-time-string

[Lars Magne Ingebrigtsen]

"Edward O'Connor" <hober0@gmail.com> writes:

> I'd like to suggest the addition of a : modifier, such that
> (format-time-string "%:z") would generate an RFC 3339-compatible time
> zone offset.

What a coincidence.  :-)  I've been playing with dropping the gnulib
strftime.c into Emacs today, and that seems to make %:z work as required:

(format-time-string "%Y-%m-%d %H:%M:%S %:z")
=> "2010-11-19 20:29:33 +01:00"

I'm guessing this will be for Emacs 24, though.

-- 
(domestic pets only, the antidote for overdose, milk.)
  larsi@gnus.org * Lars Magne Ingebrigtsen

Re: Format modifier suggestion for format-time-string

[Edward O'Connor]

Hi,

>> I'd like to suggest the addition of a : modifier, such that
>> (format-time-string "%:z") would generate an RFC 3339-compatible time
>> zone offset.
>
> What a coincidence.  :-)

No coincidence—it was that emacs-devel thread that reminded me of this
issue.

> I've been playing with dropping the gnulib strftime.c into Emacs
> today, and that seems to make %:z work as required:

I'm very happy to hear it!

> I'm guessing this will be for Emacs 24, though.

I suppose I'll go with something like this compatibility test for now:

(let ((test "%:z")) (string-equal test (format-time-string test)))


Thanks again,
Ted

Re: Format modifier suggestion for format-time-string

[MON KEY]

> I'm guessing this will be for Emacs 24, though.

This was topic was addressed circa August 2009 prior to release of Emacs 23 with
apparently too little time to integrate a similarly proposed feature.

See "Re: Can `format-time-string' produce full/extended ISO 8601 times?"
http://lists.gnu.org/archive/html/emacs-devel/2009-08/msg00262.html

Now its too little to late for 24?

Maybe we can expect this feature for Emacs 26...

--
/s_P\

Re: Format modifier suggestion for format-time-string

[Eli Zaretskii]

> Date: Sat, 20 Nov 2010 23:48:43 -0500
> From: MON KEY <monkey@sandpframing.com>
> Cc: larsi@gnus.org, hober0@gmail.com
> 
> > I'm guessing this will be for Emacs 24, though.
> [...]
> Now its too little to late for 24?

Please re-read the quotation.  It says that Emacs 24 will have it
(because 23.3 is in pretest).  It does NOT say that it's too late for
v24.

Re: Format modifier suggestion for format-time-string

[MON KEY]

On Sun, Nov 21, 2010 at 12:47 PM, Eli Zaretskii <eliz@gnu.org> wrote:
>> Now its too little to late for 24?
>
> Please re-read the quotation.  It says that Emacs 24 will have it
> (because 23.3 is in pretest).  It does NOT say that it's too late for
> v24.

OK, Great!

Sorry if I misinterpreted the intent of Lars' assumption, I hope it is
well founded.

--
/s_P\