Dave's Brain

Browse - programming tips - when is tomorrow

Date: 1998jan20
Language: C/C++


Q.  What is tomorrow?

A.  Sometimes C/C++ is so nice. Say you want to find
tomorrow's date. Do you need to make a table holding
the number of days in each month - and what about leap years?
Nope, this fairly simple code does the trick:

#include <time.h>
#include <stdio.h>

#define SECONDS_PER_DAY (60 * 60 * 24)

// Returns the date of tomorrow
void Tomorrow(int &year, int &month, int &day)
{
	time_t		now;
	struct tm	*here;

	now = time(NULL); // Get the current time
	here = localtime(&now); 
	here->tm_hour = 12; // Set to noon to handle daylight savings
	here->tm_min = here->tm_sec = 0;
	now = mktime(here) + SECONDS_PER_DAY; // The key line
	here = localtime(&now); 
	year = here->tm_year + 1900;
	month = here->tm_mon + 1;
	day = here->tm_mday;
}

main()
{
	int year, month, day;
	
	Tomorrow(year, month, day);
	printf("Tomorrow is %04d.%02d.%02d\n", year, month, day);
}

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