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The header <time.h>
declares types and functions
for manipulating date and time. Some functions process
local time, which may differ from calendar time, for
example because of time zone. clock_t
and
time_t
are arithmetic types representing times, and
struct tm
holds the components of a calendar time:
int tm_sec; |
seconds after the minute (0,61) (the committee wrongly thought there could be two leap seconds per minute) | |
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 Saving Time flag |
tm_isdst
is positive if Daylight Saving Time is in
effect, zero if not, and negative if the information is not
available.
clock
returns the processor time used by the program
since the beginning of execution, or -1
if
unavailable. clock()/CLOCKS_PER_SEC
is a time
in seconds.time
returns the current calendar time or
-1
if the time is not available. If
tp
is not NULL, the return value is also assigned to
*tp
.difftime
returns time2-time1
in
seconds.mktime
converts the local time in the structure
*tp
into calendar time in the same representation
used by time
. The components will have values
in the ranges shown. mktime
returns the
calendar time or -1
if it cannot be
represented.asctime
converts the time in the structure
*tp
into a string of the formSun Jan 3 15:14:13 1988\n\0
ctime
converts the calendar time *tp
to
local time; it is equivalent toasctime(localtime(tp))
gmtime
converts the calendar time *tp
into
Coordinated Universal Time (UTC). It returns NULL if UTC is not
available. The name gmtime
has historical
significance.
localtime
converts the calendar time *tp
into
local time.
strftime
formats date and time information from
*tp
into s
according to
fmt
, which is analagous to a printf
format. Ordinary characters (including the terminating
'\0'
) are copied into s
. Each
%c
is replaced as described below, using
values appropriate for the local environment. No more than
smax
characters are placed into
s
. strftime
returns the number of
characters, excluding the '\0'
, or zero if more than
smax
characters were produced.
%a |
abbreviated weekday name. | |
%A |
full weekday name. | |
%b |
abbreviated month name. | |
%B |
full month name. | |
%c |
local date and time representation. | |
%d |
day of the month (01-31 ). |
|
%H |
hour (24-hour clock) (00-23 ). |
|
%I |
hour (12-hour clock) (01-12 ). |
|
%j |
day of the year (001-366 ). |
|
%m |
month (01-12 ). |
|
%M |
minute (00-59 ). |
|
%p |
local equivalent of AM or PM . |
|
%S |
second (00-61 ). |
|
%U |
week number of the year (Sunday is 1st day of week)
(00-53 ). |
|
%w |
weekday (0-6 , Sunday is 0). |
|
%W |
week number of the year (Monday is 1st day of week)
(00-53 ). |
|
%x |
local date representation. | |
%X |
local time representation. | |
%y |
year without century (00-99 ). |
|
%Y |
year with century. | |
%Z |
time zone name, if any. | |
%% |
% . |
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Last modified: Fri Dec 15 2000