Zefram wrote:
This can only be done case-by-case, by examining the extensive commentary in the source files.
... and for pre-1970 data most of the commentary will boil down to "see Shanks", which has been demonstrated to be unreliable when we've checked it. There is little reason to trust that data. Shanks gives no sources -- zero -- for any of his data. As a consequence, not only are the LMT offsets unreliable, for most current entries the transition dates from LMT to standard time are unreliable. Even if we were to create an extended file that distinguishes between zones based on pre-1970 data, we shouldn't create an extended-file zone merely because it transitions away from LMT at a differing date from an existing zone, because those transition dates are typically no more reliable than the LMT offset is.