Special Topics: Date Formats
We use the Extended Date Time Format as the date standard for metadata records in The Portal to Texas History, the UNT Digital Library, and the Gateway to Oklahoma History. Although this involves some strict "behind-the-scenes" formatting, we transform the dates for display on our web sites. In most cases, item records will show dates written out in words such as:
July 14, 1822
However, some dates include symbols to show that they are approximate, uncertain, etc. If we think that the date displayed in the item record will be confusing, we add an information icon that brings you to this page for an explanation of the symbols:
X or u (letter "X" or letter "u") - An "X" takes the place of an unknown digit if only part of the date is known or is legible on the item: 191X represents the "1910s" and 1887-03-1X is March 1887 on an unknown day between the 10th and the 19th. Previous versions of the date standard used the letter "u," which may still be in some records.
~ (tilde) - The tilde notes that the date is "approximate": 1893~ is "approximately 1893" (or "circa 1893").
/ (forward slash) - A forward slash separates dates in a range: 1851/1863-08 is "1851 through August 1863."
? (question mark) - A question mark after a date notes that it may not be correct: 1758? means "this item was probably created/published in 1758, but the date is not certain."
[ ] (square brackets) - Square brackets are used for a specific unknown date among a series of possible dates or a range: [1925-07..1926-07] means "this item was created at a specific time between July 1925 and July 1926"; [1925-07,1926-07] means "July 1925 or July 1926".
% (percentage sign) - A percentage sign is used for dates that are both approximate and uncertain: 1903% means "we think this item was created sometime approximately 1903, but we aren't certain."
Also note that these examples reference when an item was created, but we also use coverage dates to represent the content of the item, so these same rules would apply. For example, a range would be "this item is about events from 1851 through August 1863" and it may or may not be the same as the creation date(s).