FW: Time zone rules change

Robert Elz kre at munnari.OZ.AU
Wed Sep 13 12:18:54 UTC 2006

    Date:        Tue, 12 Sep 2006 13:45:55 -0400
    From:        "Olson, Arthur David \(NIH/NCI\) [E]" <olsona at dc37a.nci.nih.gov>
    Message-ID:  <B410D30A78C6404C9DABEA31B54A2813997B85 at nihcesmlbx10.nih.gov>

  | From: Hammad Hassan-WHH011 [mailto:WHH011 at motorola.com]=20
  | Sent: Tuesday, September 12, 2006 1:34 PM
  | To: tz at lecserver.nci.nih.gov
  | Subject: Time zone rules change
  | Since the rules are changed lately by Egypt government, I need to change
  | the predefined rules in the time zone file, but I don't know how. I
  | found many but scattered information on the internet. So I need your
  | help.

If you tell us what the new rules are, and better, provide a web link
to some authoritative source, someone on this list will tell you exactly
what needs to change, and what it should be.

If you'd like to work it out yourself, and send in a patch, then you need
to have the timezone sources, if you don't have them already, you can fetch
the data from

You should already have the zic program to convert the rules to binary
format - if not, you can fetch the sources for that, and other stuff
that you probably won't need from

In the zone file sources (the first tar.gz above) there is a file "africa",
which has the rules for Egypt (the Africa/Cairo zone).

Look for the lines
	Rule    Egypt ...

The last two are (currently)

Rule    Egypt   1995    max     -       Apr     lastFri  0:00s  1:00    S
Rule    Egypt   1995    max     -       Sep     lastThu 23:00s  0       -

In those, change "max" to the last year that each of those rules applied,
then add two new lines

Rule    Egypt   2006    max     -       Mar     lastFri  0:00s  1:00    S
Rule    Egypt   2005    max     -       Oct     lastThu 23:00s  0       -

with the data being whatever you want for the new rule (the 2005/2006
are the first year the rule applies, perhaps 2006/2007 is what they should
be, or maybe both 2006 or 2007), the month and lastThu are obvious,
"lastFri" is used because that transition occurs at midnight at the end
of a Thursday, which is really 00:00 on the Friday (or that's what we
believe anyway).   The 's' after the times indicates that they're both
representing standard time, not summer/daylight time.

Use zic to compile the africa file  (just "zic -d. africa" will probably
work), then zdump -v Africa/Cairo to see if the transitions occur at the
correct dates and times.

When you're happy with the new rules, you can install the Africa/Cairo
file in the correct place for your system, and send the updated rules
to this list so they can be corrected for the next distribution.


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