Re: what shall we do with the drunken time_t ?

[Paul Eggert]

Couldn't asctime be causing the problem, insted of stat, gmtime etc.? The 
Microsoft documentation for asctime says that it adjusts its output according to 
local time zone settings, a behavior that disagrees with POSIX. This could 
explain the symptoms you're seeing.

https://msdn.microsoft.com/en-us/library/kys1801b.aspx
Let's put it this way: Emacs ports to mingw and does not worry about gmtime 
returning a value disagreeing with POSIX. And Emacs does not use asctime (it 
uses strftime instead).