I write a cross-platform application in which there is such a code:

auto last_write_file_time = std :: filesystem :: last_write_time (in_file_name);
Time_T TT = STD :: Chrono :: System_Clock :: To_Time_T (Last_Write_File_time);
TM Tast_WRITE_FILE_TIME_IN_TM = * STD :: Localtime (& amp; TT);

In this area, I get the time of the last file change in the structure TM .

The problem occurs when transferring this site to another platform. STD :: FileSystem :: Last_Write_Time Returns file_time_type which is an alias on STD :: Chrono :: Time_Point with some kind of predetermined parameter. That’s just this parameter varies from the compiler to the compiler and, accordingly, if in the GCC I can transfer the object Last_Write_File_Time to the function>STD :: Chrono :: System_Clock :: To_Time_T No problem, then MSVC It no longer compiles due to inconsistencies like. Is it possible to convert std :: Chrono :: Time_Point one type in another? (For example, from Std :: Chrono :: Time_point & lt; System_Clock & GT; Make Std :: Chrono :: Time_Point & LT; Steady_Clock & GT; ).

Answer 1, Authority 100%

I tried to realize different options to solve the task, in the end I bring one of the ways, it may not be the shortest, but I have under Windows / Linux on MSVC / GCC / CLANG compilers, it works right on everyone.

Conversion itself includes two lines of code that start with Static Int64_t SFClock_Diff ... and Std :: Time_T CFTime = ... , i.e. The entrance is ftime (call result std :: filesystem :: last_write_time (...) ), access CFTime Type Time_T (the latter will contain UNIX Time Stamp, i.e. number of seconds with 1970-01-01 00:00:00 ).

After this line only for informative, outputting time on the console converted to the local system.

Try online!

# include & lt; iostream & gt;
#Include & lt; Chrono & gt;
#Include & lt; fstream & gt;
#Include & lt; Filesystem & gt;
#Include & lt; Cstdint & gt;
INT MAIN ()
{
  STD :: FileSystem :: Path P = STD :: FileSystem :: Current_path () / "0413.txt";
  {STD :: OFSTREAM (P.C_STR ()). PUT ('A'); } // Create File
  AUTO FTIME = STD :: FILESSYSTEM :: Last_WRITE_TIME (P);
  STATIC INT64_T SFCLOCK_DIFF = [] {
    auto diff = int64_t (STD :: Chrono :: System_Clock :: Now (). Time_Since_epoch () / STD :: Chrono :: Milliseconds (1)) -
      INT64_T :: Clock :: Now (). Time_since_epoch () / STD :: Chrono :: Milliseconds (1));
    RETURN (Diff + (Diff & LT; 0? -500: 500)) / 1000; // Round to Nearest Second.
  } ();
  std :: time_t cftime = std :: chrono :: system_clock :: to_time_t (
    std :: chrono :: time_point & lt; std :: chrono :: system_clock & gt; (
      std :: chrono :: seconds (ftime.time_since_epoch () / std :: chrono :: seconds (1) + sfclock_diff)
    )
  );
  STD :: COUT & LT; & LT; "File write time is" & lt; & lt; std :: asctime (std :: localtime (& amp; cftime)) & lt; & lt; STD :: ENDL;
  std :: filesystem :: remove (p);
}

Conclusion:

File write time is Wed Dec 23, 2020 9:12:29