POSIX::strftime is not a good test. It was supplied binary, with Perl, and so will use "the wrong runtime" relative to Time::Piece built as an add on.

I suspected that there would be cases like this--other TZ-related calls already a part of the CORE--hence my preference that all the affected CRT routines be moved in to the win32 core, and exported and used (universally) from there.

At the moment, there are a couple of comments in T::P identifying routines that have been C&Pd from elsewhere, with the note that if they are changed here, they must be changed there also. I've seen similar notes in win32*.c/h; and others in various places in the base CORE. The myriad reinterpretations of *alloc() come to mind again.

To achieve a real fix to these type of problems, that C&P code re-use would need to be eliminated. But that's a big brief, and will be seen as only necessary to work around an MS-induced situation. Even though it is good practice to avoid C&P.