The current files have the following zone & rules: Freetown Zone Africa/Freetown -0:53:00 - LMT 1882 -0:53:00 - FMT 1913 Jun # Freetown Mean Time -1:00 SL %s 1957 0:00 SL %s Rule SL 1935 1942 - Oct 1 0:00 0 WAT Rule SL 1957 1962 - Jun 1 0:00 1:00 SLST Rule SL 1957 1962 - Sep 1 0:00 0 GMT And zic produces, among others, the following transition: Africa/Freetown Sun Jun 1 00:52:59 1913 UTC = Sat May 31 23:59:59 1913 FMT isdst=0 Africa/Freetown Sun Jun 1 00:53:00 1913 UTC = Sat May 31 23:53:00 1913 WAT isdst=0 The problem/question I have is: based on the above rules, it is not at all clear to me that Sat May 31 23:53:00 1913 should be designated 'WAT'; in fact I would have thought there would be a case for it being 'FMT' since none if the 'SL' rules apply in 1913. This is further complicated by the following rules & zones: Zone Africa/Algiers 0:12:12 - LMT 1891 Mar 15 0:01 0:09:21 - PMT 1911 Mar 11 # Paris Mean Time 0:00 Algeria WE%sT 1940 Feb 25 2:00 1:00 Algeria CE%sT 1946 Oct 7 Rule Algeria 1916 only - Jun 14 23:00s 1:00 S Rule Algeria 1916 1919 - Oct Sun>=1 23:00s 0 - which for the transition in 1911 produces 'WET'; apparently *not* using the 'S' from the first rule. And this set: Zone Africa/Accra -0:00:52 - LMT 1918 0:00 Ghana %s Rule Ghana 1936 1942 - Sep 1 0:00 0:20 GHST Rule Ghana 1936 1942 - Dec 31 0:00 0 GMT which produces 'GMT' for the transition in 1918. Can someone confirm that zic is doing the right thing (which I kind of assume it is by definition), and perhaps give me a rule to follow when performing the %s substitutions? Any help would be greatly appreciated.