On Wed, Sep 23, 2015, at 20:47, Tim Peters wrote:

[Alex]

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I added a method to datetimetester [1] to compute some overall statistics on tzfiles. My code ignores "version 2" data, so I include only transitions that fall within 32-bit time_t (1900 to 2038 range).

From staring at zic.c, looks like (so far) the data in the version 2 section is identical to that in the version 1 section, except written out in wider data formats. The pretty clear intent is that they never intend to generate explicit transitions beyond 2037 in any version,

They do have transitions for before 1901, though.

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I think this is best we can do on Windows where (IIRC) mktime does not work for times before epoch. (What about localtime?)

Windows has its own mechanism for storing timezone information, not tzdata, but no, none of the MSVCRT functions work for times before 1970.