Talk:TIMZON
DavidAcland 17:31, 26 January 2012 (UTC): I have a slight difficulty with this because I imagine that the geography for this will the slices of the world shown on Time Zone charts.
There are two points.
1. These charts are normally a Mercator projection. I suggest that we cut off the tops and bottoms of the slices at say 84 or 85 degrees North and South because few nautical charts extend further.
2. The time zones cover many jurisdictions and often different time communities. There are two major communities using Time Zone A: Central Europe and Western Africa. It is almost certain that the Summer Time start and stop will be on different dates; probably about 6 months apart in the examples I have given. Similarly Western Australia and China (UTC+8) will probably have reversed summer times. Also have a look at the slice from Finland to South Africa. Here is a link to a Time Zone Chart http://www.igooglemaps.com/gfx/map_of_timezones.jpg
The definition for Time Zone at the moment is more or less OK. However we cannot apply a SMTOFF for the whole longitude slice. So it seems to me that we need a new definition which is for a more local geography and which will probably separate the N and S hemispheres with the exception of a few areas around the equator; and the equatorial zones may not have summer time anyway. At the moment I therefore think that we do need most of the Time Zones in Jens' tables (but remove the Summer Time element) and that my construction for CATZON is incorrect.
See also my comments at Talk:CATTZN.
raphael 21:35, 26 January 2012 (UTC): How about deleting "more or less bounded by lines of longitude" from the definition?
Encoding the time zones in Jens' list is OK, with or without summer time (if "with", we may not need the summer time attributes). The list might have to be updated if and when there are changes, which might be more often than we expect, because regions do change time zones or summer time now and then - on a worldwide basis, it seems to happen quite frequently.
There is a time zone database maintained by the IANA at http://www.iana.org/time-zones
Encoders will have to be careful about what polygons they define for time zones, because of (1) the summer time issues David mentions, and (2) the time zone maps I have seen do not show maritime buondaries.