Using the datetime class

Introduction

Output Formats

The datetime class provides basic methods for getting the system date and time, and returning it in various formats.

#include <rudiments/datetime.h>
#include <rudiments/stdio.h>

int main(int argc, const char **argv) {

	// initialize an instance of datetime to the current system date/time
	datetime	dt;
	dt.initFromSystemDateTime();

	// the components of the date/time are avaialble in various formats...

	// as a string
	stdoutput.printf("date/time: %s\n\n",dt.getString());

	// including microseconds
	stdoutput.printf("date/time: %s\n\n",dt.getString(true));

	// as the number of seconds since 1970
	stdoutput.printf("seconds since 1970: %d\n\n",dt.getEpoch());

	// broken down
	stdoutput.write("date/time: ");
	stdoutput.printf("%02d/%02d/%04d %02d:%02d:%02d.%06d %s (%d)\n\n",
			dt.getMonth(),dt.getDayOfMonth(),dt.getYear(),
			dt.getHour(),dt.getMinute(),dt.getSecond(),
			dt.getMicrosecond(),
			dt.getTimeZoneString(),dt.getTimeZoneOffset());

	// additional date information
	stdoutput.write("date: ");
	stdoutput.printf("%s (%s) %d, %04d "
			"(day %d of year) (day %d of week)\n\n",
			dt.getMonthName(),dt.getMonthAbbreviation(),
			dt.getDayOfMonth(),dt.getYear(),dt.getDayOfYear(),
			dt.getDayOfWeek());
}

Date/Time Sources

An instance of the datetime class can be initialized from many different sources: the system clock, a formatted string, or from the number of seconds (and optionally microseconds) since 1970.

#include <rudiments/datetime.h>
#include <rudiments/stdio.h>

int main(int argc, const char **argv) {

	datetime	dt;

	// initialize from system date/time
	dt.initFromSystemDateTime();
	stdoutput.printf("system date/time: %s\n\n",dt.getString(true));

	// initialize from a formatted string
	dt.init("01/02/2000 03:04:05 EDT");
	stdoutput.printf("formatted string: %s\n\n",dt.getString(true));

	// initialize from the number of seconds since 1970
	dt.init(40000000);
	stdoutput.printf("seconds since 1970: %s\n\n",dt.getString(true));

	// initialize from the number of seconds and microseconds since 1970
	dt.init(40000000,100);
	stdoutput.printf("sec/usec since 1970: %s\n\n",dt.getString(true));
}

Date Math

The datetime class also provides methods for doing date math.

#include <rudiments/datetime.h>
#include <rudiments/stdio.h>

int main(int argc, const char **argv) {

	datetime	dt;

	// initialize from system date/time
	dt.initFromSystemDateTime();
	stdoutput.printf("current date/time: %s\n\n",dt.getString(true));

	// add three years, months, days,
	// hours, minutes, seconds, and microseconds
	dt.addYears(3);
	dt.addMonths(3);
	dt.addDays(3);
	dt.addHours(3);
	dt.addMinutes(3);
	dt.addSeconds(3);
	dt.addMicroseconds(3);
	stdoutput.printf("new date/time: %s\n\n",dt.getString(true));

	// subtract three years, months, days,
	// hours, minutes, seconds, and microseconds
	dt.addYears(-3);
	dt.addMonths(-3);
	dt.addDays(-3);
	dt.addHours(-3);
	dt.addMinutes(-3);
	dt.addSeconds(-3);
	dt.addMicroseconds(-3);
	stdoutput.printf("original date/time: %s\n\n",dt.getString(true));
}

Timezones

The datetime class also provides methods for getting information about timezones and converting date/times between timezones.

#include <rudiments/datetime.h>
#include <rudiments/stdio.h>

int main(int argc, const char **argv) {

	datetime	dt;

	// initialize from system date/time
	dt.initFromSystemDateTime();
	stdoutput.printf("local time: %s\n\n",dt.getString());

	// get time zone abbreviations and offsets
	const char * const *tzabbr=datetime::getTimeZoneAbbreviations();
	const int32_t *tzoff=datetime::getTimeZoneOffsets();

	// show the current time in different timezones around the world...
	while (*tzabbr && *tzabbr[0]) {

		// convert timezone
		dt.setTimeZone(*tzabbr);

		stdoutput.printf("% 14s (% 6d sec from GMT): %s\n",
					*tzabbr,*tzoff,dt.getString());

		tzabbr++;
		tzoff++;
	}
}