time_t TM Timeval and time string conversions

1, common time storage mode       1) time_t type, which is essentially a long integer representing the number of seconds from 1970-01-01 00:00:00 to the current time, if more precise is needed, You can use timeval precisely to milliseconds.       2) TM structure, which is essentially a struct that contains the time fields       struct tm {           int tm_sec;     /* seconds  after the minute - [0,59] */            int tm_min;     /* minutes after the hour -  [0,59] */           int tm_hour;     /* hours since midnight - [0,23] */            int tm_mday;    /* day of the month  - [1,31] */           int tm_mon;     /* months since january - [0,11] */           int tm_year;    /* years  since 1900 */           int tm_wday;     /* days since Sunday - [0,6] */            int tm_yday;    /* days since january  1 - [0,365] */           int tm_ isdst;   /* daylight savings time flag */            };      where tm_year represents the number of years from 1900 to the current time interval, if the value is set manually, Tm_ ISDST usually takes a value of-1.       2, commonly used time functions       time_t time (time_t *t);  // Gets the number of seconds since January 1, 1970 &NBSP;&NBsp Char *asctime (CONST&NBSP;STRUCT&NBSP;TM&NBSP;*TM);  //converts information in a structure to real-world time, displayed as a string    char  *ctime (CONST&NBSP;TIME_T&NBSP;*TIMEP);  //convert TIMEP to True world time, as a string display, it differs from asctime in that the Parameter form passed in is different     Struct tm *gmtime (CONST&NBSP;TIME_T&NBSP;*TIMEP)  //converts the time represented by time_t to a UTC time that has no time zone conversion. is a STRUCT&NBSP;TM structure pointer     struct tm *localtime (CONST&NBSP;TIME_T&NBSP;*TIMEP);  // Similar to Gmtime, but it is time-zone-converted.    time_t mktime (STRUCT&NBSP;TM&NBSP;*TM)  //convert the time of struct tm  structure to the number of seconds from 1970 to present     Int gettimeofday (STRUCT&NBSP;TIMEVAL&NBSP;*TV,&NBSP;STRUCT&NBSP;TIMEZONE&NBSP;*TZ);  // Returns the number of seconds and subtleties of the current distance 1970, and the following TZ is the time zone, generally not    double difftime (time_t time1, time_t time2);  //returns two time difference in seconds          3, time and string conversion       the header file to include is as follows        #include  <iostream>   #include  <time.h>   #include <stdlib.h>   #include  <string.h>      1) unix/ Windows Time-to-string reference code       time_t t;  //sec time    tm* local; // local time