Extended Date/Time Format Cheat Sheet

EDTF is an extension of ISO 8601, the international standard for specifying dates, to handle uncertainty and other complexities in specifying dates, especially in historical situations. The full draft specification was developed by the Library of Congress; here is a brief guide to what we are using in MormonPlaces.

2014-03-05

Typical full date, YYYY-MM-DD, must include leading zeros on month and day

2014-03

Only specified to the month; "sometime during March 2014"

2014

Only specified to the year; "sometime during 2014"

2014-21

Season (northern hemisphere): 21=Spring, 22=Summer, 23=Autumn, 24=Winter

2014~

Approximate date: "About 2014." Exact interpretation of "about" is unspecified, but +/- 2 of the most precise units given (years in this example) is a reasonable expectation.

2014?

Uncertain date: "Maybe 2014." Alternative could be anything else. Please use this sparingly, as the "anything else" is undesirable. If you have any idea of a range of possible dates, use the range form.

[2014-01-03..2014-04-15]

Range of uncertain date: "Sometime between January 3 and April 15, 2014." Note that there are exactly two periods between the dates. This is the preferred form for uncertain dates, as it is easiest for the computer to process. NOT an interval of valid dates ("during the period January 3 to April 15, 2014"); that is entered as separate start and end dates.

[..2014-04-15]

Open-ended range of uncertain date: "Sometime before April 15, 2014." In the context of MormonPlaces, the system will interpret this as anytime between 1820 and this date, so if you have any idea of a beginning of the window of possibility, please enter it.

[2014-04-15..]

Open-ended range of uncertain date: "Sometime after April 15, 2014." The system will interpret this as anytime between this date and today, so if you have any idea of an end of the window of possibility, please enter it.

unknown

The date is completely unknown, but the event is known to exist on some date. For example, we know that if a branch was organized, it had to occur on a specific day, but we are stating that we do not have any idea when that day was. Please use this sparingly, as the system cannot estimate anything from it; if you have any idea of a range of dates, use the range form.

open

Used on an ending date to assert that it still exists today.

An empty or missing date means that nobody has asserted a date, which is not the same as an unknown date or an open date. For example, if a source says "the branch was organized on April 14, 1856," and does not mention a closing date, we do not have sufficient information to assert whether the branch closed on some unknown date or exists today; just do not create an end date assertion.