[tz] NetBSD vs Darwin timezone API

[Paul Eggert]

Guy Harris wrote:
> what conclusion did we come to, if any, about the lifetime of memory pointed to by tm_zone?

In the reference implementation and in NetBSD, the lifetime is until the 
corresponding timezone_t object is passed to tzfree. Come to think of it, that 
argues against spontaneous changes to timezone_t objects unless the changes 
never obsolete any existing abbreviations.

I don't know about Darwin. I hope the tm_zone lifetime is not erratic (i.e., 
until the next time the system randomly decides to change time zones); that 
would be bad.