Hi, from Hong Kong Observatory ( http://www.weather.gov.hk/gts/time/Summertime.htm ), 30 Dec 73 to 20 Oct 74 is "summer time" period. While the enties in tzcode "asia" files: Rule HK 1965 1977 - Apr Sun>=16 3:30 1:00 S Rule HK 1965 1977 - Oct Sun>=16 3:30 0 - Would you help to check if the entries in tzcode should be updated accordingly? thx -- Regards, King-On Yeung