Unix time-dependent structures and functions __ functions

about Unix Time ①time_t Data Typetypedef long int time_t; Used to store the number of seconds from 1970 to the present. ②timeval Structural Bodystruct Timeval
{
Long tv_sec; /* SEC * *
Long tv_usec; /* microsecond * *
};
Structure struct Timeval, it is precise to subtle. ③tm Structural Bodystruct TM
{
int tm_sec; /* seconds, normal range 0-59, but allowed to 61*/
int tm_min; * * minutes, 0-59*/
int tm_hour; * * hours, 0-23*/
int tm_mday; /* Day, that is, the first day of one months, 1-31*/
int Tm_mon; /* month, from January, 0-11*/1+p->tm_mon;
int tm_year; * * year, from 1900 so far has been many years * * * 1900+ p->tm_year;
int tm_wday; * * Week, the first day of the week, from Sunday, 0-6*/
int tm_yday; * * FROM January 1 this year to the current number of days, range 0-365*/
int tm_isdst; * * Daylight Saving Time flag/
};
It is particularly noteworthy that the year has been years since 1900, rather than direct storage such as 2011, the month starting from 0, 0 means January, week is also starting from 0, 0 for Sunday, 1 for Monday.
④ commonly used time functions:#include <time.h>
1. Asctime

Char *asctime (const struct tm* timeptr); The time that the information in the structure is converted to the real world, displayed as a string
2. CTime

Char *ctime (const time_t* TIMEP); Convert TIMEP to really world time, in string display, it differs from asctime in the form of parameters passed in, converted format: "Wed June 21:49:08 1993\n"
3. Difftime

Double Difftime (time_t time1, time_t time2); Returns the number of seconds that differ by two times
4. Gettimeofday int gettimeofday (struct timeval* tv,struct timezone*);
Returns the number of seconds and subtleties in the current distance of 1970, and the TZ is the time zone, generally not
5. Gmtime

struct tm* gmtime (const time_t* TIMEP); Converts the time represented by time_t to UTC without time zone conversion, and is a struct TM structure pointer
6. LocalTime

struct tm* localtime (const time_t* TIMEP); Similar to Gmtime, but it is time to transition through time zone.
7. Mktime

time_t mktime (struct tm* timeptr); Converts the time of the struct TM structure to the number of seconds from 1970 to the present
8. Time

time_t time (time_t* t); Gets the number of seconds since January 1, 1970. 9. Strftime

size_t strftime (char *s, size_t max, const char *format, const struct TM *TM); Converts the TM structure body to a string. Strptime

Char *strptime (const char *s, const char *format, struct TM *tm); Converts a string to a TM structure body. ⑤ a piece of code:

#define _xopen_source
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

int main (void)
{
           struct TM TM;
           Char buf[255];
           memset (&tm, 0, sizeof (struct TM));
           Strptime ("2001-11-12 18:31:01", "%y-%m-%d%h:%m:%s", &TM);
           Strftime (buf, sizeof (BUF), "%d%b%Y%h:%m", &TM);
           Puts (BUF);
           Exit (exit_success);
}