Help With Understanding the Binary Files

Bill Seymour stdbill.h at
Wed Dec 9 14:09:42 UTC 2009

Could somebody please help me interpret the tz
binary files?

I'm having trouble understanding what to do with
the two arrays that follow the leap second array.

1.  tzfile.h says that they're "indexed by type";
but I don't see anything in the "type" (which I
take to mean what tzfile.5 calls "struct ttinfo")
that could be used as such an index.  Does
"indexed by type" mean "having the same index
as the type", in other words, the value from
the array following the transition time array?

2.  tzfile.h seems to imply that these booleans
indicate how I should interpret the values in
the array of transition times.  Is that correct?
If so, how do I calculate standard time while
DST is being observed given that the SAVE column
in the Rule has been lost?  Do I assume that the
offset for DST is always exactly 1 hour?  What
about solar89, etc.?

3.  tzfile.5 says that these "are used when a time
zone file is used in handling POSIX-style time zone
environment variables."  Does that mean that the
"transition times" are the ones in the TZ variable,
not the array of transition times in the file
(so my question 2 is moot)?

I'm very confused. 8-(


--Bill Seymour

More information about the tz mailing list