Articulated lorries (semi trucks) are much bigger and slower than F1 or Indy cars. Diesel-electric freight trains even bigger and slower.

But, it doesn't mean that any time someone has a minor problem with their truck (the satnav in my truck sometimes looses the gps signal), or train (the horn on my loco sometimes sqeaks rather than bellows), that the appropriate response is: Trucks (trains) are big and slow; what you need is an F1 car!

To advise which of those two extremes, or where between them, is the most appropriate tool for the OPs problem, requires that you first have some information regarding that problem. And then the best advice will depend upon the problem being tackled.

It's all about giving an appropriate response to the question asked. For the OPs question, that was that his apparent expectation that changing the value of $ENV{TZ} would directly and immediately affect the behaviour of localtime, is misplaced.

Descending into a rant that he should not be using threads, when there is zero information in his OP of what or how he is using threads, is simply an inappropraite response. Doing so in the basis of your near total misunderstanding of the subject of your rant is ...