Extended Date Time Format (EDTF)

OSUL is implementing EDTF dates (https://www.loc.gov/standards/datetime/edtf.html) in Digital Collections (DC) in the Date Created field. This date standard allows entry of dates that are approximate, date spans, etc. Later on, DC will include a feature to convert these dates to a human-readable display format in DC (see "example - display" column).

NOTE: When entering dates in an Excel spreadsheet, it is recommended to format date columns as "Text". Otherwise, Excel may reformat dates according to its own standards.

situation	encoding format	example - encoded	example - display	notes
year known	yyyy	1989	1989
year and month known	yyyy-mm	1989-03	March 1989
year, month, and day known	yyyy-mm-dd	1989-03-22	March 22, 1989
year given is uncertain	yyyy?	1989?	1989?	The "?" character may occur only at the end of the date string and apply to the entire date.
year and month given are uncertain	yyyy-mm?	1989-03?	March 1989?	The "?" character may occur only at the end of the date string and apply to the entire date.
year, month, and day given are uncertain	yyyy-mm-dd?	1989-03-22?	March 22, 1989?	The "?" character may occur only at the end of the date string and apply to the entire date.
year given is approximate	yyyy~	1989~	circa 1989	The "~" character may occur only at the end of the date string and apply to the entire date.
year and month given are approximate	yyyy-mm~	1989-03~	circa March 1989	The "~" character may occur only at the end of the date string and apply to the entire date.
year, month, and day given are approximate	yyyy-mm-dd~	1989-03-22~	circa March 22, 1989	The "~" character may occur only at the end of the date string and apply to the entire date.
date range is known	yyyy/yyyy	1989/2019	1989 to 2019	Also works with YYYY-MM and YYYY-MM-DD W3C formats (e.g. "1989-03-22/2019-08-14")
date range is approximate or uncertain	yyyy-mm~/yyyy-mm~	1989-03~/2019-08~	circa March 1989 to August 2019	Also works with "?" character.
general time period is known but the specific year or decade is unspecified	yyyX	198X	1980s	Also works at a century level (e.g. "19XX" = "1900s")
date range where the beginning and end dates are known but specific years and decades are unspecified	yyyX/yyXX	198X/20XX	1980s to 2000s	Does not work with yyyy-mm and yyyy-mm-dd formats