TimeZone

• timezonedatabase.9janu317pm.cs
  
• samplezones.zip
  
• cpzones

1. Class PointInTime, an abstract representation of time independent of its representation in time zones (or in local Smalltalk systems).
   
2. A time zone class hierarchy beginning with class LocalTimeTransform (this name is chosen to avoid conflicts with class TimeZine in VisualWorks, which already provides limited time zone support in a class of this name). Subclasses include
   
   • NaiveTimeZone, which behaves like a Smalltalk system with no time zone rules
     
   • OSTimeZone, which uses a plugin to ask the underlying operating system about time zone offsets (useful only on Unix based systems)
     
   • TimeZoneRuleSet, which represents a time zone in the time zone database, and knows how to create instances of itself by parsing compiled time zone files in tzfile(5) format, commonly found on newer Unix-like systems.
   
   
3. TimeZoneDatabase, which maintains a dictionary of time zones, and answers UTC offsets and leap second offsets for its time zones at any point in time (a PointInTime).
   
4. A plugin to support operating system queries for the OSTimeZone class. This is optional, and OSTimeZone attempts to default to sensible behavior in the absence of the plugin.

1. Download the change set and example time zone files. Unzip the time zone files in your Squeak directory. This will give you some representative time zone files (copied from a Linux distribution and renamed so they will work on other kinds of computers). You may also want to download the cpzones script, which is useful for copying time zone files from a Unix system into files with names which will work on other systems.
   
2. Load the change set, then try the class examples in TimeZoneDatabase. The results you see will be relative to the time zone for Detroit, Michigan, USA.
   
3. Set your default time zone with "TimeZoneDatabase systemDatabase defaultLocation: 'my-preferred-timezone-name'". You may need to get a more complete set of time zone files first (see below).
   
4. Read the class documentation for more information. Try using the object explorer on your time zone database to get a better understanding of what it's doing. There are some class side example methods in class TimeZoneDatabase to get you started.

1. If you are using a Linux, FreeBSD, or other system with time zone files in the /usr/share/zoneinfo directory, you can execute the expression "TimeZoneDatabase buildSystemDatabase" to load a complete database of the world's time zones from your system database files.
   
2. If your computer understands how to do gzip and tar, download a set of compiled time zone files from a Linux or FreeBSD distribution. For example, a full set of compiled time zone files, in the form of a gzipped tar archive, may be found at
   ftp://ftp.cdrom.com/pub/linux/slackware-current/slakware/a1/zoneinfo.tgz
   
3. Convince someone with a web server running on some flavor of Unix to add a to the files in their web server's /usr/share/zoneinfo directory so that you can download them.
   
4. Find a friend who uses Linux and ask for a copy of the files in the /usr/share/zoneinfo directory. If your computer is a Mac or Windows machine, copy the time zone files using a naming convention which your computer can handle (that is, no directories with "/" in the path names). The cpzones shell script will help your friend do this for you.
   
5. The real source of all this time zone data is the ~ftp/pub directory of elsie.nci.nih.gov, which provides current time zone data, documentation, and source code for C language time zone utilities.