Re: Full Julian date in date command formatting options? (original) (raw)

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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 http://libvirt.org

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