C++标准库中用来计算时间差的函数
头文件 < time.h >

double difftime(
   time_t timer1,
   time_t timer0
);
double _difftime32(
      __time32_t timer1,
   __time32_t timer0
);
double _difftime64(
   __time64_t timer1,
   __time64_t timer0
);

C++标准库用来格式化输出时间字符串
头文件 < time.h >

size_t strftime(
   char *strDest,
   size_t maxsize,
   const char *format,
   const struct tm *timeptr
);
size_t _strftime_l(
   char *strDest,
   size_t maxsize,
   const char *format,
   const struct tm *timeptr,
   _locale_t locale
);
size_t wcsftime(
   wchar_t *strDest,
   size_t maxsize,
   const wchar_t *format,
   const struct tm *timeptr
);
size_t _wcsftime_l(
   wchar_t *strDest,
   size_t maxsize,
   const wchar_t *format,
   const struct tm *timeptr,
   _locale_t locale
);

The formatting codes for strftime are listed below:

%a
    Abbreviated weekday name

%A
    Full weekday name

%b
    Abbreviated month name

%B
    Full month name

%c
    Date and time representation appropriate for locale

%d
    Day of month as decimal number (01 – 31)

%H
    Hour in 24-hour format (00 – 23)

%I
    Hour in 12-hour format (01 – 12)

%j
    Day of year as decimal number (001 – 366)

%m
    Month as decimal number (01 – 12)

%M
    Minute as decimal number (00 – 59)

%p
    Current locale's A.M./P.M. indicator for 12-hour clock

%S
    Second as decimal number (00 – 59)

%U
    Week of year as decimal number, with Sunday as first day of week (00 – 53)

%w
    Weekday as decimal number (0 – 6; Sunday is 0)

%W
    Week of year as decimal number, with Monday as first day of week (00 – 53)

%x
    Date representation for current locale

%X
    Time representation for current locale

%y
    Year without century, as decimal number (00 – 99)

%Y
    Year with century, as decimal number

%z, %Z
    Either the time-zone name or time zone abbreviation, depending on registry settings; no characters if time zone is unknown

%%
    Percent sign