NAME

ctime, localtime, gmtime, asctime, timezone, dysize −  convert date and time to ASCII

SYNOPSIS

char ∗ctime(clock)
long ∗clock;

#include <sys/time.h>

struct tm ∗localtime(clock)
long ∗clock;

struct tm ∗gmtime(clock)
long ∗clock;

char ∗asctime(tm)
struct tm ∗tm;

char ∗timezone(zone, dst)

int dysize(y)
int y;

DESCRIPTION

ctime retrieves a time pointed to by clock such as returned by time(3C) or the tv_sec element of the struct timeval (filled in by gettimeofday(2)), that is, the number of seconds since Jan. 1, 1970, 00:00, Greenwich Mean Time. It converts this value into ASCII, and returns a pointer to a 26-character string of the form:

Sun Sep 16 01:03:52 1973\n\0

Each field has a constant width.  Localtime and gmtime return pointers to structures containing the broken-down time.  Localtime corrects for the time zone and possible daylight savings time; gmtime converts directly to GMT, which is the time UNIX uses.  Asctime converts a broken-down time to ASCII and returns a pointer to a 26-character string. 

The structure declaration from the include file is:

struct tm {
inttm_sec;
inttm_min;
inttm_hour;
inttm_mday;
inttm_mon;
inttm_year;
inttm_wday;
inttm_yday;
inttm_isdst;
};

These quantities give the time on a 24-hour clock, day of month (1-31), month of year (0-11), day of week (Sunday = 0), year − 1900, day of year (0-365), and a flag that is nonzero if daylight saving time is in effect. 

When local time is called for, the program consults the system to determine the time zone and whether the U.S.A., Australian, Eastern European, Middle European, or Western European daylight saving time adjustment is appropriate.  The program knows about various peculiarities in time conversion over the past 10-20 years. 

Timezone returns the name of the time zone associated with its first argument, which is measured in minutes westward from Greenwich.  If the second argument is 0, the standard name is used, otherwise the Daylight Saving version.  If the required name does not appear in a table built into the routine, the difference from GMT is produced; e.g.  in Afghanistan timezone(-(60∗4+30), 0) is appropriate because it is 4:30 ahead of GMT and the string GMT+4:30 is produced. 

Dysize returns the number of days in the argument year, either 365 or 366. 

SEE ALSO

gettimeofday(2), time(3C)

BUGS

The return values point to static data.  The contents are overwritten by each call. 

Sun Release 3.0β  —  Last change: 23 August 1983