C language Time Function

1. Time () gets the current time

Time_t timer;

Time (& timer );

Equivalent to timer = Time (null); or timer = time (0 );

It can be used to generate random numbers.

Srand (unsigned) time (0 ));

2. localtime () converts a timestamp into the format of year, month, and day

3. ctime () converts a timestamp to a string expressed by year, month, and day.

char* ctime (const time_t * timer);

Struct TM * date; time_t now; time (& now); Date = localtime (& now); // ctime () demo char * datestr; datestr = ctime (& now ); // mktime demo time_t restm = mktime (date); // strftimecout <now <Endl; cout <date-> tm_year <"" <date-> tm_mon <"" <date-> tm_mday <Endl; cout <datestr <Endl; cout <restm <Endl;

4 differtime returns the time (in seconds)

double difftime (time_t end, time_t beginning);

5 strftime ()

size_t strftime (char* ptr, size_t maxsize, const char* format,                 const struct tm* timeptr );

Format and display the time pointed by timeptr in pstr.

Specifier	Replaced	Example
%a	Abbreviated weekday name *	Thu
%A	Full weekday name *	Thursday
%b	Abbreviated month name *	Aug
%B	Full month name *	August
%c	Date and Time Representation *	Thu Aug 23 14:55:02 2001
%C	Year divided by 100 and truncated to INTEGER (00-99)	20
%d	Day of the month, zero-padded (01-31)	23
%D	ShortMM/DD/YYDate, equivalent%m/%d/%y	08/23/01
%e	Day of the month, space-padded ( 1-31)	23
%F	ShortYYYY-MM-DDDate, equivalent%Y-%m-%d	2001-08-23
%g	Week-based year, last two digits (00-99)	01
%G	Week-based year	2001
%h	Abbreviated month name * (same%b)	Aug
%H	Hour in 24 h format (00-23)	14
%I	Hour in 12 h format (01-12)	02
%j	Day of the year (001-366)	235
%m	Month as a decimal number (01-12)	08
%M	Minute (00-59)	55
%n	New-line character ('\n')
%p	AM or PM designation	PM
%r	12-hour clock time *	02:55:02 pm
%R	24-hourHH:MMTime, equivalent%H:%M	14:55
%S	Second (00-61)	02
%t	Horizontal-Tab character ('\t')
%T	ISO 8601 time format (HH:MM:SS), Equivalent%H:%M:%S	14:55:02
%u	ISO 8601 weekday as number with Monday1(1-7)	4
%U	Week number with the first Sunday as the first day of week one (00-53)	33
%V	ISO 8601 week number (00-53)	34
%w	Weekday as a decimal number with Sunday0(0-6)	4
%W	Week number with the first Monday as the first day of week one (00-53)	34
%x	Date representation *	08/23/01
%X	Time Representation *	14:55:02
%y	Year, last two digits (00-99)	01
%Y	Year	2001
%z	ISO 8601 offset from UTC in timezone (1 minute = 1, 1 hour = 100) If timezone cannot be termined, no characters	+100
%Z	Timezone name or abbreviation * If timezone cannot be termined, no characters	CDT
%%	A%Sign	%

* The specifiers marked with an asterisk (*) are locale-dependent.
Note: yellow rows indicate specifiers and sub-specifiers introduced by c99. since c99, two locale-specific
Modifiers can also be inserted between the percentage sign (%) And the specifier proper to request an alternative format, where applicable:

Modifier	Meaning	Applies
E	Uses the locale's alternative representation	%Ec %EC %Ex %EX %Ey %EY
O	Uses the locale's alternative numeric symbols	%Od %Oe %OH %OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy