There's some super useful data in the MARC fixed fields too -- more useful
than the semi-transcribed values in 260c, although it's also a pain to
access/transform to something reasonably machine actionable.

Here's the code from traject that tries to get a reasonable date out of
marc fixed fields, falling back to 260c if it needs to.
https://github.com/traject/traject/blob/e98fe35f504a2a519412cd28fdd97dc514b603c6/lib/traject/macros/marc21_semantics.rb#L299-L379

There are already quite a few places in MARC for dates. It's just they're
all weird. You're making up yet a new kind of date to your own local
meaning and specs. I doubt there's an existing MARC field you can put it in
where it won't just add to the confusion. (obligatory reference to
https://xkcd.com/927/).

I'd just put it in a 9xx or xx9 field of your choosing, they are reserved
for local use.

On Mon, Jul 11, 2016 at 3:19 PM, Joy Nelson <[log in to unmask]>
wrote:

> Hi Eric-
> Are you planning on storing the 'normalized' dates for ever in the MARC?
> i.e. leave the c1900 in the 260$c and have 1900 in another place?
>
> I think what you do depends on your ILS and tools.  My first reaction would
> be to stash the date in an unused subfield in the 260.  If your system
> allows you to add 'non standard' subfields, you could use 260$z to stash
> it.
>
> But, then I start to think that might rankle some catalogers to have 'non
> standard' date data in the 260 (or 264).  I would probably then look at
> using one of the local use tags.  901-907, 910, or 945-949.  You could be
> the date in $a and even a brief description in a second subfield.
> 901$a1900$bnormalized date for project XYZ -initials/date
>
> -Joy
>
> On Mon, Jul 11, 2016 at 12:51 PM, Eric Lease Morgan <[log in to unmask]>
> wrote:
>
> > I’m looking for date fields.
> >
> > Or more specifically, I have been given a pile o’ MARC records, and I
> will
> > be extracting for analysis the values of dates from MARC 260$c. From the
> > resulting set of values — which will include all sorts of string values
> > ([1900], c1900, 190?, 19—, 1900, etc.) — I plan to normalize things to
> > integers like 1900. I then want to save/store these normalized values
> back
> > to my local set of MARC records. I will then re-read the data to create
> > things like timelines, to answer questions like “How old is old?”, or to
> > “simply” look for trends in the data.
> >
> > What field would y’all suggest I use to store my normalized date content?
> >
> > —
> > Eric Morgan
> >
>
>
>
> --
> Joy Nelson
> Director of Migrations
>
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