...

I have one comment regarding the timezone file format.

Why not use a few of 20 remaining bytes in tzh_reserved field for a magic number that would be unique to timezone data files? 4 bytes at the beginning of the file would be great, but if you're concerned about space then 2 bytes would do the job if selected carefully.

I would like to add that we need it to be PERSISTENT: even if timezone would not exist anymore its magic number should be preserved. It makes possible to use them for database storage.

I'm unclear here. One possibility would be to drop a string such as try man tzfile (or something shorter) into each timezone file at a fixed place, so that the UNIX "file" command (in conjunction with an appropriate "magic" entry) could identify it. (A string such as that above might have the benefit of making the file self-documenting.) But the suggestion above seems to involve generating particular tags for particular files. Can anyone make things clearer? --ado