[Tagging] Date formatting proposal

[Laurence Penney]

I'm posting here a link to a proposal for date formatting that I just added to the start_date wiki page:

http://wiki.openstreetmap.org/wiki/Key:start_date

The motivator was the discovery of many tag values of unfeasible heterogeneity in start_date. Taginfo reports 18313 usages (2814 distinct), of which these are examples of values other than simple 4-digit years[1]:

1986-08-21 29/09/2006 05/01/2005 2002-12-31 03/12/2004 2001-07-12 20101012 Nov␣2007 1.1.2012 1966␣restauriert 0200-12-29 0085-12-12 4.12.10 Spring␣2010 -2000 08.2010 18.␣jahrh. 0008-09-16 2009-09-10␣09:00:00␣+0200 1966-08-XX 19th␣century February␣2000 2007-XX-XX 1700-talet 1960s c.␣1903 1758;␣1909 12.␣April␣2008 1869-19?? Early␣18th␣century 1984;1988;1986;1985;1989;1989;1986 Summer␣of␣2009 13/07/2006;␣05/01/2005 circa␣1820 5/1923␣-␣10/1926 623AD Late␣11th␣to␣early␣12th␣century -3 <1878 1959-09-01;1960-08-19;1960-08-31;2006-10-26 XVème 3100␣BC

... and my favourite: octobre

So it's clear there's a demand for: exact dates; general approximations; approximations to the month, season, century; before <date> and after <date>; early <period> and late <period>, maybe also mid <period>; date ranges; multiple values; BC and AD.

We can probably ignore: exact times. They should go in their own time tags, if anyone wants them.

In my own historic photo tagging I have found numerous captions that date pictures with varying degrees of precision using similar non-standard means. I then turn these into a date tag, trying to capture as much of that vague richness as possible. The proposed scheme is similar to what I have been using and parsing successfully.

Comments welcome! Please follow up either here or on the Discussion page on the wiki.

- L

[1] http://taginfo.openstreetmap.de/keys/start_date