On Wed, Jan 11, 2012 at 20:58:38 +0000, Donald MacQueen wrote:
1) What is the difference between America/Detroit and posix/America/Detroit? The test cases I have written return what looks like the same DST record for a given date no matter which one I use. Under what circumstances would I use posix/America/Detroit?
The actual distinction is betweeh "posix" and "right", which differ in whether they account for the existence of leap seconds when counting seconds-since-the-epoch. On a particular system, the default one of those two choices is found in the timezones without a prefix; that default will presumably always match either "posix" or "right". So, for example, on my Debian system there are three "America/Detroit" files. If I run md5sum on each of the three, I see that the no-prefix one matches the "posix' one: $ md5sum `locate Detroit` 17b0eead3047f767a1d8eefa5151308e /usr/share/zoneinfo/America/Detroit 17b0eead3047f767a1d8eefa5151308e /usr/share/zoneinfo/posix/America/Detroit 4c99fc9061e7353cf5310f582a16e428 /usr/share/zoneinfo/right/America/Detroit Assuming your system is the same, it would obviously make sense that your test cases would all return the same result for the two zones you were trying -- but if you compare America/Detroit and right/America/Detroit, you should find some differences...
2) Where is the format of the tz source filesdescribed? Specifically what do SAVE and Letter/S mean below? I am also interested in what the Link format is.
# Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S Rule Nic 1979 1980 - Mar Sun>=16 0:00 1:00 D Rule Nic 1979 1980 - Jun Mon>=23 0:00 0 S
The zic man page (zic.8) documents these fields. Nathan ---------------------------------------------------------------------------- Nathan Stratton Treadway - nathanst@ontko.com - Mid-Atlantic region Ray Ontko & Co. - Software consulting services - http://www.ontko.com/ GPG Key: http://www.ontko.com/~nathanst/gpg_key.txt ID: 1023D/ECFB6239 Key fingerprint = 6AD8 485E 20B9 5C71 231C 0C32 15F3 ADCD ECFB 6239