C++ LANGUAGE STANDARD LIBRARY

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C++ LANGUAGE STANDARD LIBRARY

STANDARD LIBRARY 


The C++ standard library does not provide a proper date type. 
C++ inherits the structs and functions for date and time 
manipulation from C. To access date and time related functions 
and structures, you would need to include <ctime> header 
file in your C++ program. 

There are four time-related types: clock_t, time_t, size_t, and tm. 
The types - clock_t, size_t and time_t are capable of representing 
the system time and date as some sort of integer. 

The structure type tm holds the date and time in the form of a 
C structure having the following elements: 

struct tm { 
  int tm_sec;   // seconds of minutes from 0 to 61 
  int tm_min;   // minutes of hour from 0 to 59 
  int tm_hour;  // hours of day from 0 to 24 
  int tm_mday;  // day of month from 1 to 31 
  int tm_mon;   // month of year from 0 to 11 
  int tm_year;  // year since 1900 
  int tm_wday;  // days since sunday 
  int tm_yday;  // days since January 1st 
  int tm_isdst; // hours of daylight savings time 
} 
Following are the important functions, which we use while working with 
date and time in C or C++. All these functions are part of standard C 
and C++ library and you can check their detail using reference to C++ 
standard library given below. 



SN             Function & Purpose 
1             time_t time(time_t *time); 
                   This returns the current calendar time of the system 
                   in number of seconds elapsed since January 1, 1970. 

                   If the system has no time, .1 is returned. 
2             char *ctime(const time_t *time); 
                   This returns a pointer to a string of 
                   the form day month year hours:minutes:seconds year\n\0. 


3             struct tm *localtime(const time_t *time); 
                   This returns a pointer to the tm structure 
                   representing local time. 


4             clock_t clock(void); 
                   This returns a value that approximates the amount 
                   of time the calling program has been running. A value 
                   of .1 is returned if the time is not available.  
 
5             char * asctime ( const struct tm * time ); 
                   This returns a pointer to a string that contains 
                   the information stored in the structure pointed to 
                   by time converted into the form: day month date 
                   hours:minutes:seconds year\n\0 

6             struct tm *gmtime(const time_t *time); 
                   This returns a pointer to the time in the form of 
                   a tm structure. The time is represented in Coordinated 
                   Universal Time (UTC), which is essentially Greenwich Mean Time (GMT). 


7             time_t mktime(struct tm *time); 
                   This returns the calendar-time equivalent of the 
                   time found in the structure pointed to by time. 

8             double difftime ( time_t time2, time_t time1 ); 
                   This function calculates the difference 
                   in seconds between time1 and time2. 

9             size_t strftime(); 
                   This function can be used to format 
                   date and time in a specific format.