C language Time Function

Source: Internet
Author: User
Tags iso 8601 month name

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

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