OpenHistoricalMap/Tags/Key/start_date:edtf
 start_date:edtf
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| Description |
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Approximate or uncertain date when the feature came into existence. 
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| Group: lifecycle |
| Used on these elements |
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| Requires |
| Useful combination |
| Status: de facto |
| Tools for this tag |
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]](https://upload.wikimedia.org/wikipedia/commons/thumb/f/f3/Mary%2C_Help_of_Christians_Church_%28Fairborn%2C_Ohio%29_-_cornerstone%2C_1970.jpg/180px-Mary%2C_Help_of_Christians_Church_%28Fairborn%2C_Ohio%29_-_cornerstone%2C_1970.jpg)
"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]](https://upload.wikimedia.org/wikipedia/commons/thumb/e/ed/The_Town_Hall%2C_Plaque_%28geograph_2074147%29.jpg/117px-The_Town_Hall%2C_Plaque_%28geograph_2074147%29.jpg)
"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=1750~
"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]](https://upload.wikimedia.org/wikipedia/commons/thumb/e/e3/San_Jose%2C_CA_USA_-_panoramio.jpg/120px-San_Jose%2C_CA_USA_-_panoramio.jpg)
"before 1800":
start_date=1800
start_date:edtf=/1800 or [..1800][3]
!["1970": start_date=1970 start_date:edtf=1970[1]](/wiki/File:Mary,_Help_of_Christians_Church_(Fairborn,_Ohio)_-_cornerstone,_1970.jpg)
!["between 1906 and 1908": start_date=1908[2] start_date:edtf=1906/1908 or [1906..1908][3]](/wiki/File:The_Town_Hall,_Plaque_(geograph_2074147).jpg)
!["before 1800": start_date=1800 start_date:edtf=/1800 or [..1800][3]](/wiki/File:San_Jose,_CA_USA_-_panoramio.jpg)
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