RTClib.h

// A library for handling real-time clocks, dates, etc.
// 2010-02-04 <jc@wippler.nl> http://opensource.org/licenses/mit-license.php

// Simple general-purpose date/time class (no TZ / DST / leap second handling!)
class DateTime {
public:
    DateTime (long t =0);
    DateTime (uint16_t year, uint8_t month, uint8_t day,
                uint8_t hour =0, uint8_t min =0, uint8_t sec =0);
    DateTime (const char* date, const char* time);

    uint16_t year() const       { return 2000 + yOff; }
    uint8_t month() const       { return m; }
    uint8_t day() const         { return d; }
    uint8_t hour() const        { return hh; }
    uint8_t minute() const      { return mm; }
    uint8_t second() const      { return ss; }
    uint8_t dayOfWeek() const;

    // 32-bit times as seconds since 1/1/2000
    long get() const;   

protected:
    uint8_t yOff, m, d, hh, mm, ss;
};

// RTC based on the DS1307 chip connected via I2C and the Wire library
class RTC_DS1307 {
public:
    static void begin() {}
    static void adjust(const DateTime& dt);
    static DateTime now();

    // utility functions
    static uint8_t bcd2bin (uint8_t val) { return val - 6 * (val >> 4); }
    static uint8_t bin2bcd (uint8_t val) { return val + 6 * (val / 10); }
};

// RTC based on the PCF8563 chip connected via I2C and the Wire library
// contributed by @mariusster, see http://forum.jeelabs.net/comment/1902
class RTC_PCF8563 {
public:
    static void begin() {}
    static void adjust(const DateTime& dt);
    static DateTime now();

    // utility functions
    static uint8_t bcd2bin (uint8_t val) { return val - 6 * (val >> 4); }
    static uint8_t bin2bcd (uint8_t val) { return val + 6 * (val / 10); }
};

// RTC using the internal millis() clock, has to be initialized before use
// NOTE: this clock won't be correct once the millis() timer rolls over (>49d?)
class RTC_Millis {
public:
    static void begin(const DateTime& dt) { adjust(dt); }
    static void adjust(const DateTime& dt);
    static DateTime now();

protected:
    static long offset;
};