arduino code from SEEED for precision i2c realtime clock with corrected calibration constant.

realtimeclock.ino

/****************************************************************************/
//  Function: Set time and get the time from RTC chip(PCD85063TP) and display
//            it on the serial monitor.
//  Hardware: Grove - RTC v2.0
//  Arduino IDE: Arduino-1.6.6
//  Author:   lambor
//  Date:    June 14,2016
//  Version: v1.0
//  by www.seeedstudio.com
//
//  This library is free software; you can redistribute it and/or
//  modify it under the terms of the GNU Lesser General Public
//  License as published by the Free Software Foundation; either
//  version 2.1 of the License, or (at your option) any later verscion.
//
//  This library is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//  Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public
//  License along with this library; if not, write to the Free Software
//  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
//
/****************************************************************************/
#include <Wire.h>
#include "PCF85063TP.h"

PCD85063TP xclock;//define a object of PCD85063TP class
void setup()
{
  Serial.begin(9600);
  xclock.begin();
 
  xclock.stopClock();
  xclock.fillByYMD(2018,2,7);//Jan 19,2013
  xclock.fillByHMS(00,25,45);//15:28 30"
  xclock.fillDayOfWeek(WED);//Saturday
  xclock.setTime();//write time to the RTC chip
  xclock.startClock();


  xclock.setcalibration(1, 32768);  // Setting offset by xclock frequency
  uint8_t ret = xclock.calibratBySeconds(0, -0.000041);
  Serial.print("offset value: ");
  Serial.print("0x");
  Serial.println(ret, HEX);
 
}
void loop()
{
  printTime();
  delay(1000);
}
/*Function: Display time on the serial monitor*/
void printTime()
{
  xclock.getTime();
  Serial.print(xclock.hour, DEC);
  Serial.print(":");
  Serial.print(xclock.minute, DEC);
  Serial.print(":");
  Serial.print(xclock.second, DEC);
  Serial.print("  ");
  Serial.print(xclock.month, DEC);
  Serial.print("/");
  Serial.print(xclock.dayOfMonth, DEC);
  Serial.print("/");
  Serial.print(xclock.year+2000, DEC);
  Serial.print(" ");
  Serial.print(xclock.dayOfMonth);
  Serial.print("*");
  switch (xclock.dayOfWeek)// Friendly printout the weekday
  {
    case MON:
      Serial.print("MON");
      break;
    case TUE:
      Serial.print("TUE");
      break;
    case WED:
      Serial.print("WED");
      break;
    case THU:
      Serial.print("THU");
      break;
    case FRI:
      Serial.print("FRI");
      break;
    case SAT:
      Serial.print("SAT");
      break;
    case SUN:
      Serial.print("SUN");
      break;
  }
  Serial.println(" ");
}