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Re: Full Julian date in date command formatting options?

From: Eric Blake
Subject: Re: Full Julian date in date command formatting options?
Date: Fri, 11 Oct 2013 16:04:48 -0600
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[re-adding the list, with permission]

On 10/11/2013 01:53 PM, Reed Underwood wrote:
>> For example, The Julian Date for 00:30:00.0 January 1, 2013 is
>> 2456293.520833.
>> If the astronomical term is what you want, then maybe you really do have
>> a format that cannot be expressed in any existing notation, and maybe it
>> really is worth burning a % notation.  But how common is the
>> Astronomical Julian Date in shell programming?
> I instinctively turned to 'date' for the full Julian date for astronomical 
> purposes,
> but I concede that this is not an incredibly common use case. I thought I'd
> pitch it to see if there's any interest. If it's too much of an edge case,
> no problem. I just noticed there's no '%J' and thought it might be alright
> to roll it in, figuring that I'm likely not the *only* person who's ever
> wondered if 'date' could do this (but maybe I am!).

It might be worth asking on address@hidden if the glibc folks are
interested in an extension for Julian date, as the date(1) command
heavily copies from glibc's strftime(3).  If we burn a letter in
coreutils without their consent, and they later choose to give that
letter a different meaning, then we're stuck - so we'd need to
coordinate the addition across both projects if there is enough
consensus that it is worth adding.

> Definitely, the '%j' form gives you the day of the year, which is likely
> more commonly used (though I'm not sure in what context).

At this point, I'm guessing that there's probably not enough demand to
warrant adding astronimical Julian Date to the general-purpose date
command, but it may also help to collect a few more opinions from others
before giving up on the attempt.

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library

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