Hi, I am trying to understand the database file format and have a question regarding the rule definition of Asia/Tokyo and Asia/Karachi. Both time zones seem to be valid but I cannot see that from their definition in the database. Let's look at Asia/Tokyo only, but Asia/Karachi is similar... # Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S Rule Japan 1948 only - May Sun>=1 2:00 1:00 D Rule Japan 1948 1951 - Sep Sat>=8 2:00 0 S Rule Japan 1949 only - Apr Sun>=1 2:00 1:00 D Rule Japan 1950 1951 - May Sun>=1 2:00 1:00 D # Zone NAME GMTOFF RULES FORMAT [UNTIL] Zone Asia/Tokyo 9:18:59 - LMT 1887 Dec 31 15:00u 9:00 - JST 1896 9:00 - CJT 1938 9:00 Japan J%sT So Asia/Tokyo references the ruleset "Japan" which is only defined for the years 1948 - 1951. Wouldn't that mean that Asia/Tokyo is only valid during those years? Especially, it references a substring with "J%sT", where does this substring come from for any other year? Thanks a lot, Joachim