DigistumpArduino/digistump-avr/libraries/TinyRTClib/examples/datecalc/datecalc.pde

// Simple date conversions and calculations

#include <TinyWireM.h>
#include "TinyRTClib.h"

void showDate(const char* txt, const DateTime& dt) {
    Serial.print(txt);
    Serial.print(' ');
    Serial.print(dt.year(), DEC);
    Serial.print('/');
    Serial.print(dt.month(), DEC);
    Serial.print('/');
    Serial.print(dt.day(), DEC);
    Serial.print(' ');
    Serial.print(dt.hour(), DEC);
    Serial.print(':');
    Serial.print(dt.minute(), DEC);
    Serial.print(':');
    Serial.print(dt.second(), DEC);
    
    Serial.print(" = ");
    Serial.print(dt.unixtime());
    Serial.print("s / ");
    Serial.print(dt.unixtime() / 86400L);
    Serial.print("d since 1970");
    
    Serial.println();
}

void setup () {
    Serial.begin(115200);
    
    DateTime dt0 (0, 1, 1, 0, 0, 0);
    showDate("dt0", dt0);

    DateTime dt1 (1, 1, 1, 0, 0, 0);
    showDate("dt1", dt1);

    DateTime dt2 (2009, 1, 1, 0, 0, 0);
    showDate("dt2", dt2);

    DateTime dt3 (2009, 1, 2, 0, 0, 0);
    showDate("dt3", dt3);

    DateTime dt4 (2009, 1, 27, 0, 0, 0);
    showDate("dt4", dt4);

    DateTime dt5 (2009, 2, 27, 0, 0, 0);
    showDate("dt5", dt5);

    DateTime dt6 (2009, 12, 27, 0, 0, 0);
    showDate("dt6", dt6);

    DateTime dt7 (dt6.unixtime() + 3600); // one hour later
    showDate("dt7", dt7);

    DateTime dt8 (dt6.unixtime() + 86400L); // one day later
    showDate("dt8", dt8);

    DateTime dt9 (dt6.unixtime() + 7 * 86400L); // one week later
    showDate("dt9", dt9);
}

void loop () {
}