[kronolith] Timezones with dates before 1970

[Chuck Hagenbuch]

Community-

I'm looking for some feedback on this ticket:

http://bugs.horde.org/ticket/?id=5593

Basically, if you have both a recent glibc OR are on Windows, and  
aren't using PHP 5, dates before 1970 and after 2038 don't work with  
unix timestamps. The ticket above is for parsing vTimezone data, which  
suffers from this problem depending on the dates in the timezone rules.

Does anyone have a sense of how often vTimezone data has dates before  
1970 in it? I'd rather let this go if it's an edge case, since PHP 5  
will handle it just fine anyway, but if we have to, we can put in some  
workaround code.

Thanks,
-chuck