From: Dave Kelly[SMTP:dkelly@lhr-sys.DHL.COM] Date: Monday, August 11, 1997 2:30 PM We decided to use the HP-UX timezone name from the tztab file as a reference to a timezone since it seemed as good as anything else. We have now realised that the entries we have as default in tztab are far from complete. Do you know where we could get hold of a tztab file which has a complete list of entries? I don't know the HP-UX tztab scheme. However, I do know the Olson tz scheme, which is available on most recent Unix hosts (BSD, Linux, SGI, Sun) and I understand that HP-UX now has (optional?) support for the Olson tz scheme in /opt/dce/lib/zoneinfo. The Olson tz scheme is fairly complete for time zone histories after 1970. We do not want to maintain multiple tztab entries for countries which use the same zone - i.e. we want to have a single entry for all the countries which use CET/CEST. Here's what I think you're asking for. If you're interested only in times now and in the future, then the Olson database contains too many names, partly because it goes back to 1970 and thus must track historical changes, and partly because it insists on at least one name per country. You want just one distinct name for each time zone future, regardless of country. In that case, what you need is a way to look at the Olson database, find all the distinct time zone futures in it (starting with 1997, say), and choose a canonical name for each distinct future. Choosing the canonical name requires human judgment, but the rest of this task can be done automatically. Here's a shell script that does the automatic part; it assumes the existence of an `md5' command that prints a checksum, but you can substitute your own checksum command if you don't have md5. This script assumes that the only thing that matters about a time zone is its UTC offset; it ignores the time zone name (e.g. "EST", "EDT") and whether the time is daylight-saving time. Also, watch out for a bug in the script: it thinks Asia/Hong_Kong differs from Asia/Shanghai because Hong Kong's time zone abbrevation changed from HKT to CST when it reverted to China last month (and similarly for Macao in 1999). #! /bin/sh thisYear=`date +%Y` TZDIR=/usr/local/etc/zoneinfo TZs=`cd $TZDIR && find [A-Z]* -type f -print | sort` selectZdumpInfo='{ if ('$thisYear'<=$6) print $3, $4, $5, $6, $10, $11, $12, $13 }' for TZ in $TZs do echo "`zdump -v $TZDIR/$TZ | awk "$selectZdumpInfo" | md5` $TZ" done | sort | awk '{ checksum = $1 TZ = $2 if (checksum != oldChecksum) print "" print TZ oldChecksum = checksum }' This script outputs a series of TZ groups, each group preceded by an empty line, and each group consisting of one or more lines specifying a TZ value. All the TZ values in a group have the same UTC offset from this year on. I ran this program on the latest TZ data. The output started like this: Asia/Alma-Ata Australia/LHI Australia/Lord_Howe Etc/GMT+8 SystemV/PST8 America/Belize America/Costa_Rica America/El_Salvador America/Guatemala America/Regina America/Swift_Current America/Tegucigalpa Canada/East-Saskatchewan Canada/Saskatchewan Etc/GMT+6 Pacific/Galapagos SystemV/CST6 Asia/Novosibirsk Asia/Omsk ... That is, Asia/Alma-Ata has a unique time zone future; Australia/LHI and Australia/Lord_Howe have the same time zone future (not too surprising, since they're aliases); Etc/GMT+8 and SystemV/PST8 are identical but no actual locations are 8 hours behind UTC all year so we can ignore it; parts of Central America and Saskatchewan are 6 hours behind UTC all year; and so forth. After quickly looking through the above output, I suggest the following set of 95 entries from the tz database with unique UTC offset futures. For example, this list uses the name `Europe/Paris' for CET/CEST (though perhaps `Europe/Brussels' would be more appropriate :-). Africa/Addis_Ababa Africa/Algiers Africa/Cairo Africa/Casablanca Africa/Johannesburg Africa/Tripoli Africa/Windhoek America/Adak America/Anchorage America/Asuncion America/Buenos_Aires America/Caracas America/Chicago America/Cuiaba America/Denver America/Godthab America/Grand_Turk America/Halifax America/Havana America/Indianapolis America/Los_Angeles America/Miquelon America/Montevideo America/New_York America/Phoenix America/Port-au-Prince America/Regina America/Santiago America/Sao_Paulo America/St_Johns Asia/Alma-Ata Asia/Amman Asia/Anadyr Asia/Aqtau Asia/Aqtobe Asia/Baghdad Asia/Baku Asia/Beirut Asia/Bishkek Asia/Calcutta Asia/Dacca Asia/Damascus Asia/Irkutsk Asia/Jakarta Asia/Jerusalem Asia/Kabul Asia/Kamchatka Asia/Karachi Asia/Katmandu Asia/Krasnoyarsk Asia/Magadan Asia/Novosibirsk Asia/Rangoon Asia/Shanghai Asia/Tehran Asia/Tokyo Asia/Ulan_Bator Asia/Vladivostok Asia/Yakutsk Asia/Yekaterinburg Asia/Yerevan Atlantic/Azores Atlantic/Cape_Verde Atlantic/Stanley Australia/Adelaide Australia/Brisbane Australia/Darwin Australia/Hobart Australia/Lord_Howe Australia/Sydney Europe/Bucharest Europe/Istanbul Europe/London Europe/Minsk Europe/Moscow Europe/Paris Europe/Riga Europe/Samara Europe/Simferopol Europe/Warsaw Pacific/Auckland Pacific/Chatham Pacific/Easter Pacific/Gambier Pacific/Guadalcanal Pacific/Honolulu Pacific/Kiritimati Pacific/Marquesas Pacific/Norfolk Pacific/Noumea Pacific/Pitcairn Pacific/Rarotonga Pacific/Samoa Pacific/Tongatapu Pacific/Wake