How to Read the tz Database Source Files | tz database
HowtoReadthetzDatabaseHowtoReadthetzDatabase[1]SourceFilesbyBillSeymourThispageusestheAmerica/ChicagoandPacific/Honoluluzonesasexamplesofhowtoinfertimesofdayfromthetzdatabase[2]sourcefiles.Itmightbehelpful,butnotabsolutelynecessary,forthereadertohavealreadydownloadedthelatestreleaseofthedatabaseandbecomefamiliarwiththebasiclayoutofthedatafiles.Theformatisexplainedinthe“manpage”fortheziccompiler,zic.8.txt,inthecodesubdirectory.We’llbeginbytalkingabouttherulesforchangingbetweenstandardanddayli...
How to Read the tz Database How to Read the tz Database[1] Source Files by Bill SeymourThis page uses the America/Chicago and Pacific/Honolulu zones as examples of how to infer times of day from the tz database[2] source files. It might be helpful, but not absolutely necessary, for the reader to have already downloaded the latest release of the database and become familiar with the basic layout of the data files. The format is explained in the “man page” for the zic compiler, zic.8.txt, in the code subdirectory.
We’ll begin by talking about the rules for changing between standard and daylight saving time since we’ll need that information when we talk about the zones.
First, let’s consider the special daylight saving time rules for Chicago (from the northamerica file in the data subdirectory):
From the Source File #Rule NAME FROM TO - IN ON AT SAVE LETTER Rule Chicago 1920 only - Jun 13 2:00 1:00 D Rule Chicago 1920 1921 - Oct...