time/rtc/source/main.c

#include <3ds.h>
#include <stdio.h>
#include <time.h>
 
const char* const months[12] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
 
const char* const weekDays[7] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
 
const u16 daysAtStartOfMonthLUT[12] =
{
    0   % 7, //january    31
    31  % 7, //february   28+1(leap year)
    59  % 7, //march      31
    90  % 7, //april      30
    120 % 7, //may        31
    151 % 7, //june       30
    181 % 7, //july       31
    212 % 7, //august     31
    243 % 7, //september  30
    273 % 7, //october    31
    304 % 7, //november   30
    334 % 7  //december   31
};
 
static inline bool isLeapYear(int year)
{
    return (year%4) == 0 && !((year%100) == 0 && (year%400) != 0);
}
 
static inline int getDayOfWeek(int day, int month, int year)
{
    //http://en.wikipedia.org/wiki/Calculating_the_day_of_the_week
    day += 2*(3-((year/100)%4));
    year %= 100;
    day += year + (year/4);
    day += daysAtStartOfMonthLUT[month] - (isLeapYear(year) && (month <= 1));
    return day % 7;
}
 
int main(int argc, char **argv)
{
    // Initialize services
    gfxInitDefault();
 
    //Initialize console on top screen. Using NULL as the second argument tells the console library to use the internal console structure as current one
    consoleInit(GFX_TOP, NULL);
 
    printf("\x1b[30;16HPress Start to exit.");
 
    // Main loop
    while (aptMainLoop())
    {
        //Scan all the inputs. This should be done once for each frame
        hidScanInput();
 
        //hidKeysDown returns information about which buttons have been just pressed (and they weren't in the previous frame)
        u32 kDown = hidKeysDown();
 
        if (kDown & KEY_START) break; // break in order to return to hbmenu
 
        //Print current time
        time_t unixTime = time(NULL);
        struct tm* timeStruct = gmtime((const time_t *)&unixTime);
 
        int hours = timeStruct->tm_hour;
        int minutes = timeStruct->tm_min;
        int seconds = timeStruct->tm_sec;
        int day = timeStruct->tm_mday;
        int month = timeStruct->tm_mon;
        int year = timeStruct->tm_year +1900;
 
        printf("\x1b[1;1H%02i:%02i:%02i", hours, minutes, seconds);
        printf("\n%s %s %i %i", weekDays[getDayOfWeek(day, month, year)], months[month], day, year);
 
        // Flush and swap framebuffers
        gfxFlushBuffers();
        gfxSwapBuffers();
 
        //Wait for VBlank
        gspWaitForVBlank();
    }
 
    // Exit services
    gfxExit();
 
    return 0;
}