It would be useful to specify the locations and times of events in a manner that could be automatically harvested, searched, queried, compared, etc.
What is needed 
- YYYY-MM-DD HH:MM:SS using UTC times and Gregorian calendar; single time point or start and end times (see eg DLESE metadata standards)
- Timezone is secondary information which may be useful for display, but won't affect the actual time defined.
- What about pre-Gregorian dates?
- Also need to have vaguer descriptions for geologic eras, etc
- Some time ranges may be open-ended; for instance the time ref for a city might extend from its founding through the present, assumed to extends an indefinite period into the future.
- Descriptive name (not normative)
- Latitude and longitude: as point and/or minimal bounding rectangle and/or polygon approximation (see eg DLESE metadata standards)
- Encoding system (eg. WGS84 vs. GPS)
- Altitude, in meters. For some events an altitude range would be useful. (Flights, mountain climbing, spelunking records :)
- Planet! Think of moon landings, mars rovers, etc. For events not on/near earth, we need to be able to specify where they did take place. Planets & moons may have lat/long/altitude; there's also deep space, asteroids... how to specify these?
An article may define a geospatial reference as being that of the page's subject overall; it may also have additional references for particular sub-regions or sub-events.
References to outside/intersecting events should probably be left to the software to determine via linking.
Perhaps, using for Weather. Should be better then this (Commons:WeatherMaps).
Are these references going to be purely for querying and harvesting, or might there be reason to generate maps/timelines to display in articles? Could be useful.
The preferred method of displaying times could be a new user preference, since Americans are used to mm-dd-yyyy and Europeans prefer dd.mm.yyyy.
What are these things going to look like? They can't be too intimidating or overly break up the flow of article text (like current HTML table markup does).
We don't want no XML.
- Many time references are written into the text of articles. Would it be useful to have some way of making these explicit to avoid duplication? Or would this make the text too complicated?
See also 
- Alexandria Digital Library Gazetteer Server
- GeoURL.org (ICBM Address Server) - Location-to-URL mapping search engine
- Getty Thesaurus of Geographic Names - very extensive search engine for places
What the XML world is up to on this 
- Draft for the Usage of the Coverage-Element of the Dublin_Core-Standard , allready rather old (1997) but quit elaborated
- RSS provides a Module for the Dublin_Core
- The Geography Markup Language provides a very flexible framework for expressing geographic features that can have a relationship to time
- GeoInfo project
- Placetime.com is intended to be a URI-space for representations of times and places