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Public-images-osm logo.svg start_date
Connel bridge plate.jpg
Date when feature opened or the construction of the feature finished. Edit or translate this description.
Group: Properties
Used on these elements
may be used on nodesmay be used on waysmay be used on areasmay be used on relations
Status: de facto


start_date=* can be used to indicate the date the feature opened or construction of the feature finished (i.e. started to exist as feature).


Exact dates

Dates use the ISO 8601-01 system, which is based on the Gregorian calendar. Be aware that for exact dates there are differences of up to 11 days between the Gregorian and Julian calendars and that different countries switched to the Gregorian calendar over a 400 year period.


  • start_date=2010 ; where the year is known, but no more
  • start_date=0897 (for 897 CE)
  • start_date=1848-07 ; where the year and month are known
  • start_date=2010-03-31 ; for where the full date is known, using the format yyyy-mm-dd

Caution: ISO8601 uses the format yyyy-mm-dd, not the model of mm-dd-yyyy or dd-mm-yyyy


Often a date will not be known exactly. In which case some of the following can be used:

  • start_date=~1855 (some time around 1855)
  • start_date=1860s (during the 1860s (i.e 1860 → 1869 inclusive))
  • start_date=~1940s (probably during the 1940s)
  • start_date=480 BC (for something that happened in that year)
  • start_date=before 1855 (during 1854 or before)
  • start_date=before 1910-01-20 (before a specific date - possibly when a photo was taken)
  • start_date=after 1823 (after 1 January 1823 - possibly based on the year in which a map was produced)
  • start_date=C18 (during the 18th century)
  • start_date=mid C14 (some time during the middle of the 14th century)
  • start_date=late 1920s
  • start_date=~C13 (probably in the 13th century)
  • start_date=1914..1918 indicates some time during WW1.
  • start_date=2008-08-08..2008-08-24 indicates some time during the Beijing Olympics.
  • start_date=mid C17..late C17
  • start_date=j:1918-01-31 (a date using the Julian calendar, equivalent to 1918-02-13 in the Gregorian calendar)
  • start_date=jd:2455511 (Using the Julian day system, equivalent to 2010-11-10 in the Gregorian calendar)
  • Muslim calendar?

'1800s' means the years 1800-1809, not 1800-1899. Prefixes of 'early ', 'mid ', 'late ', 'before ' or 'after ' to indicate those things.

Avoid seasons. For example 'summer 1998' as these vary between the hemispheres. Consider using '1998-05..1998-08' for summer in the northern hemisphere.

BCE can be used in place of BC. AD is assumed where BC is not used but optionally be included.

Avoid multiple entries, for example 2010-08-01;2010-08-19 without providing at least an explanation in a note.

Marking a civilization, period and era

You can also add information by setting the following keys (no need to restrict them to features with a historic=*):


Some values drawn from a review of Taginfo: start_date, on 2010-11-10 show severe heterogeneity.

End date and alternatives

end_date=* is sometimes used to mark end of existence/validity of features. Without additional precautions the use of end_date is considered a trolltag and the use of it is likely to break existing routing and rendering software if used without namespace prefixes on main tags. For alternatives see Comparison of life cycle concepts.

Open Historical Map uses end_date extensively.

Possible Tagging Mistakes

If you know places with this tag, verify if it could be tagged with another tag.
Automated edits are strongly discouraged unless you really know what you are doing!
If you know places with this tag, verify if it could be tagged with another tag.
Automated edits are strongly discouraged unless you really know what you are doing!

See also

External links

Maps showing start_date

Modules for working with start_date values

HTML5 dates