I forgot the header file.
/*
DS1337.h - library for DS1337 rtc
*/
// ensure this library description is only included once
#ifndef DS1337_h
#define DS1337_h
// include types & constants of Wiring core API
#include <WConstants.h>
// include types & constants of Wire ic2 lib
#include <Wire/Wire.h>
#define DS1337_SEC 0
#define DS1337_MIN 1
#define DS1337_HR 2
#define DS1337_DOW 3
#define DS1337_DATE 4
#define DS1337_MTH 5
#define DS1337_YR 6
#define DS1337_BASE_YR 2000
#define DS1337_CTRL_ID B1101000
// Define register bit masks
#define DS1337_CLOCKHALT B10000000
#define DS1337_LO_BCD B00001111
#define DS1337_HI_BCD B11110000
#define DS1337_HI_SEC B01110000
#define DS1337_HI_MIN B01110000
#define DS1337_HI_HR B00110000
#define DS1337_LO_DOW B00000111
#define DS1337_HI_DATE B00110000
#define DS1337_HI_MTH B00110000
#define DS1337_HI_YR B11110000
#define DS1337_ARLM1 0x07
#define DS1337_ARLM1_LO_SEC B00001111
#define DS1337_ARLM1_HI_SEC B01110000
#define DS1337_ARLM1_LO_MIN B01110000
#define DS1337_ARLM1_HI_MIN B00001111
#define DS1337_SP 0x0E
#define DS1337_SP_EOSC B10000000
#define DS1337_SP_RS2 B00010000
#define DS1337_SP_RS1 B00001000
#define DS1337_SP_INTCN B00000100
#define DS1337_SP_A2IE B00000010
#define DS1337_SP_A1IE B00000001
#define DS1337_STATUS 0x0F
#define DS1337_STATUS_OSF B10000000
#define DS1337_STATUS_A2F B00000010
#define DS1337_STATUS_A1F B00000001
// library interface description
class DS1337
{
// user-accessible "public" interface
public:
DS1337();
void get(int *, boolean);
int get(int, boolean);
void set(int, int);
void start(void);
void stop(void);
unsigned char getRegister(unsigned char registerNumber);
void setRegister(unsigned char registerNumber, unsigned char registerValue);
void unsetRegister(unsigned char registerNumber, unsigned char registerMask);
// library-accessible "private" interface
private:
byte rtc_bcd[7]; // used prior to read/set DS1337 registers;
void read(void);
void save(void);
};
extern DS1337 RTC;
#endif