OpenHistoricalMap/Tags/Key/start_date:edtf

start_date:edtf
Description
Approximate or uncertain date when the feature came into existence.
Group: lifecycle
Used on these elements
Requires
start_date=*
Useful combination
end_date:edtf=*
Status: de facto
start_date:edtf=* More details at taginfo
Tools for this tag
overpass-turbo

This subkey of start_date=* qualifies the feature's start date in the Extended Date Time Format, a profile of ISO 8601 that supports times of day, uncertainty, approximation, and seasons.

How to tag

Tag the EDTF start date in start_date:edtf=*. For backwards compatibility, also set start_date=* to the most accurate date that can be expressed in that key's more rigid YYYY-MM-DD format. Do not set start_date=* to OpenStreetMap's approximations syntax. OHM rejects this syntax in favor of EDTF in start_date:edtf=*.

Examples

• 
  "1970":
  start_date=1970
start_date:edtf=1970^[1]
• 
  "Sunday May 1, 1960 1 P. M.":
  start_date=1960-05-01
start_date:edtf=1960-05-01T13:00
• 
  "circa 1849":
  start_date=1849
start_date:edtf=1849~
• 
  "between 1906 and 1908":
  start_date=1908^[2]
  start_date:edtf=1906/1908 or [1906..1908]^[3]
• 
  "mid 18th century":
  start_date=1750
start_date:edtf=1730/1770 or [1730..1770]^[3]
• 
  "1890s":
  start_date=1895
start_date:edtf=189X
• 
  "the fall of 1814":
  start_date=1814
start_date:edtf=1814-23
• 
  "thought to have been built in 1804":
  start_date=1804
start_date:edtf=1804?
• 
  "before 1800":
  start_date=1800
start_date:edtf=/1800 or [..1800]^[3]
• 
  "late in 1887":
  start_date=1887
start_date:edtf=1887-39
• 
  "early April 1992":
  start_date=1992-04
start_date:edtf=1992-04-01/1992-04-10^[4]

Software support

In iD, you can click the button in the Start Date field to set an EDTF date. iD validates this date and will warn if it is malformed or the start_date=* falls outside the range of possible dates described by the EDTF date. If the start_date=* is expressed in OSM's "approximations" format, iD will flag it as an invalid date and offer to replace it with the equivalent start_date:edtf=* tag in EDTF format.

No renderer has built-in support for EDTF dates yet.

See also

• end_date:edtf=*
• Open Historical Map/Dates And Times
• Open Historical Map/Tags/Proposed/Tag:start date=datespec

Notes and references

External links

• Extended Date/Time Format (EDTF) Specification
• ANTLR EDTF parser
• Bayou City DAMS Map date input guidelines from the University of Houston