Approximate Dates

Sources cited in the Syriac Reference Portal frequently give approximate or estimated dates in a variety of prose formats. In order to enable these approximate dates to be processed as machine-readable data, contributors should translate approximate prose dates into ranges with numeric values which reflect the level of precision in the source document.

In general the following prose conventions will be encoded into numeric values according to the following guidelines:

  • Xth century -- use an 100-year range
  • X-Yth centuries -- use an 100-year range for each century
  • first/second half of Xth century -- use a 50-year range
  • early/late Xth century -- use a 50-year range
  • mid-Xth century -- use a 50-year range
  • first/last quarter of Xth century -- use a 25-year range
  • beginning of Xth century -- use a 25-year range at the beginning of the century plus an additional 15-year margin into the previous
  • end of Xth century -- use a 25-year range at the end of the century plus an additional 15-year margin into the next

These numeric values may be combined as in the following cases:

  • Early to mid Xth Century -- use a 75-year range
  • late Xth century to early Yth century -- use a 100-year range across two centuries
  • late Xth century to first quarter of Yth century -- use a 50-year range at the end of the century plus an additional 25-year margin into the next

NOTE: The ranges corresponding to approximate dates are not mutually exclusive (e.g. early overlaps with mid), nor should they be, since they are by nature not precise information. Accordingly, we have choosen round numbers to begin and end ranges, e.g. 0400-0450 and 0450-0500. The overlap is intended to reflect the imprecision of "first half of the fifth century" which a human author may not intend to end precisely in 0449.

Circa, ?, Floruit, etc.

For dates whose ambiguity has been emphasized by the use of “circa”, “?”, or similar wording, contributors should add additional margins of 15, 25, or 50 years to the dates (contributors may use their discretion in proportion to the size of the date ranges and the uncertainty of the date). Thus “circa Xth century” would be rendered as an 200 year range with 50-year margins on either side of the century in question. Floruit dates should be considered in this same class of highly ambiguous dates. Accordingly a floruit date of “fl. Xth century” should be rendered as an 200-year range, even though the subject is not likely to have flourished for 200 years. Given the highly ambiguous nature of dates in ancient and medieval sources, our editorial preference is to avoid creating a level of precision not supported by the sources.

Exceptions for Precise Dates

These guidelines do not apply when a more precise range for a date is known (e.g. between years x and y). In such a case, these specific years should be used instead of the above ranges.

In general, approximate dates will be encoded into TEI using the @not-before and @not-after attributes (which corresponds to terminus ante/post quem). In cases where specific dates are known or where a choice of date is more appropriate than a range, the @when attribute and multiple <date> elements may be used.


Prose Description Not-Before Date Not-After Date Notes
4th century 0300 0400 Full century.
4th century? 0250 0450 Question mark shows greater uncertainty.
probably 4th century 0250 0450 "Probably" shows greater uncertainty.
first half of 5th century 0400 0450
second half of 6th century 0550 0600
probably 2nd half of 9th cent. 0825 0925 "Probably" shows greater uncertainty.
mid-7th century 0625 0675
mid-7th century? 0610 0690 Question mark shows greater uncertainty.
early 8th century 0700 0750
early 8th century? 0675 0775 Question mark shows greater uncertainty.
late 9th century 0850 0900
late 9th century? 0825 0925 Question mark shows greater uncertainty.
10th/11th century 0900 1100 Two centuries.
ca. 10th/11th century? 0850 1150 Clearly very uncertain.
10th - early 11th century 0900 1050
late 10th/11th century 0950 1100
first quarter of 11th century 1000 1025
last quarter of 12th century 1175 1200
late 13th - early 14th century 1250 1350
end of the 14th century 1375 1410
between 327-335 0327 0335 Use dates specified.
826? 0811 0841 15 year margin on either side.
before 359 (blank) 0359 Terminus ante quem. No way to know how long before.
shortly before 1252 1237 1252 15 year margin.
after 829 0829 (blank) Terminus post quem. No way to know how long after. Contributors may, however, add a Not-After end date here by means of inference. For example if a source is reporting on events which have come to conclusion before the publication of the source, the Not-After date may be inferred to be at least the publication date of the source.
shortly after 1587 1587 1602 15 year margin
probably after 829 0814 (blank) Not certain date is after 829, so 15 year margin before.
ca. 1842 1827 1857 15 year margin on either side.
ca. 381? 0356 0406 Question mark shows greater uncertainty: 25 year margin on either side.
ca. 491-496 0476 0511 15 year margin on from each end of the range.
ca. 13th century 1150 1350
between the 10th and beginning of the 13th cent. 0900 1225 Quite a range!
around the end of the 16th and the first decades of the 17th cent. 1575 1630
1864/5 1864 1865 One year or the other. Note: This only applies to consecutive dates.
1887/1890 1887 1890
200? 2000 2009 This use of the ? can be misleading. It does not mean "perhaps 200" but rather "2000-something." This usage is rare, so contributors should consult with an editor on how to encode.