Use of custom date with non-Gregorian calendars

[dlschwartz]

See https://tei-c.org/release/doc/tei-p5-doc/en/html/ref-att.datable.custom.html

I think we should be using @when-custom, @notBefore-custom, and @notAfter-custom with non-Gregorian dates.

[davidamichelson]

Here is what we have done in Manuscripts: https://docs.google.com/document/d/175Yx1uf_HaXRA6O36p83vf-ECFWLGFNbUXoDF7ffVDs/edit

Use the <origin> element to provide the date in which the manuscript was written and, when known, the place. The element <origDate> can be used in combination with the @calendar attribute.

<history>
<origin>
<origDate notBefore="1600" notAfter="1700" calendar="Gregorian">xviith century</origDate>
</origin>
</history>

Valid values for @calendar should always be “Gregorian”
1. Gregorian [=A.D.]

Other calendars can be added using @datingMethod (see below)

2. Julian
3. AM
4. Hijri-shamsi
5. Hijri-qamari [=A.H.]
6. Coptic-EoM
7. Alexandrian
8. Iranian-Yazdigird
9. Iranian-Jalali
10. Spanish
11. Ilahi
12. Hindu
13. Seleucid [=A. Gr.]
14. unknown
15. other

@calendar should always be used when specific, rather than estimated, dates are mentioned.

Additionally, a number of attributes are used to qualify the <origDate> element:
1. @notBefore specifies the earliest possible date in standard form (yyyy-mm-dd)
2. @notAfter specifies the latest possible date in standard form (yyyy-mm-dd)
3. @from indicates the starting point of the period in standard form (yyyy-mm-dd)
4. @to indicates the ending point of the period in standard form (yyyy-mm-dd)
5. @when supplies the value of the date or time in a standard form (yyyy-mm-dd)

These attributes should ALWAYS contain Gregorian dates. If a non-Gregorian date is used, these attributes should be appended with “-custom” (@notBefore-custom, @notAfter-custom, @from-custom, @to-custom, @when-custom) and the element should include the @datingMethod attribute to clarify the non-Gregorian calendar:

Example for <origin>:
<origin>
     <origDate when=”0615” calendar=”Gregorian”>A. D. 615</origDate>
     <origDate when-custom=”0926” datingMethod=”Seleucid”>A. Gr. 926</origDate>
</origin>
All dates should be rendered in an ISO format and approximate dates should be converted to numeric values following the Syriaca.org Dates Guidelines: http://htmlpreview.github.io/?https://github.com/srophe/syriaca/blob/Edits-to-Date-Policy/dates.html

NB: Only dates relevant to the origin of the manuscript should appear here. All other dates tagged elsewhere in the document should be marked with the element <date> and not reproduced under <origin>.

When a date is given in a chronogram, use the @rend attribute with a value of "chronogram:

Example for chronogram:
<origDate datingMethod="Hijri-qamari" when-custom="1351" rend="chronogram"> في عام غفر انك =1351</origDate>

In order to refer to a particular item in a manuscript with multiple works, the date should be nested within a <ref> element with the attribute @target="#msItem id" [see 2. Linking with the TEI document above]

Example of dates for multiple works:
<origin>
     <ref target="#a1">
          <origDate datingMethod="Hijri-qamari" when-custom="1091">1091</origDate>
          <origPlace xml:lang="eng">Cairo</origPlace>
          <origPlace xml:lang="ara">القاهرة</origPlace>
     </ref>
</origin>

[wlpotter]

Cf. https://github.com/srophe/britishLibrary-data/issues/529 and especially this comment