How unsafe is std::localtime?

Question

Hiya!
I was just completed an example on using streams and when I went to compile, Visual Studio complained that localtime was depreciated and considered unsafe and that I should consider using localtime_s instead.

Can anyone tell me "how" unsafe it is?
I.e Is it a massive weakness if I use this method. Should I listen, can people run arbitrary code through this or can they just give the program a new time?

I also read that microsoft are the ones who have depreciated it, and that localtime is still standard c++.
\Who is right? - So confused. -> when am I not though <-

Here is the example:
https://code.sololearn.com/c60QW3uVGxYd/#cpp

Answer 1

This is what I got from stack exchange, related to your question.

http://stackoverflow.com/questions/17982366/localtime-and-asctime-are-unsafe-but-the-safe-functions-dont-have-the-same-par

http://stackoverflow.com/questions/14386923/localtime-vs-localtime-s-and-appropriate-input-arguments

Answer 2

Yeah I saw those as well. I havent yet seen (or understand is probably a better description) what a person can do with it that makes it deemed unsafe.

Is a buffer overflow possible?
Or is only the returned time that is able to be changed?

Answer 3

FYI: Just for reference I found this: not sure if it will answer my question. But it may be interesting. (1 hour long presentation) - so yeah, I haven't finished watching it yet!

"A C++14 approach to dates and times"
https://www.youtube.com/watch?v=tzyGjOm8AKo