JeeLabs Precision RTC Module

I'm not sure I have got the grasp of these modules.

How does something like this look?

/* Copyright (c) 2014 Your Name. See the file LICENSE for copying permission. */
/*
Quick description of my module...
*/

//private
var C = {
  dstStatus : ,          // description
  rtcDate: ,     // description
  rtcTime: ,  // description
};

//private functions
// Convert Decimal value to BCD
function dec2bcd(val) {
  return parseInt(val, 16);
}

// Convert BCD value to decimal
function bcd2dec(val) {
  return ("0"+val.toString(16)).substr(-2);
}

//DST
function isDST(date,month,dow)
    {
        //January, february, and december are out.
        if (month < 3 || month > 11) {
    return false;
    }
        //April to October are in
        if (month > 3 && month < 11) {
    return true;
    }
    var previousSunday = day - dow;
        //In march, we are DST if our previous sunday was on or after the 8th.
        if (month == 3) {
    return previousSunday >= 8;
    }
        //In november we must be before the first sunday to be dst.
        //That means the previous sunday must be before the 1st.
        return previousSunday <= 0;
    }

//public
DS3231.prototype.C = {
  i2c_address = 0x68,
  rtcTime : ,          // description
  rtcDate : ,     // description
  rtcDay : ,  // description
  dstShift :
};

//public functions
/* Put most of my comments outside the functions... */
DS3231.prototype.setDate = function(date,month,year) {
  I2C1.writeTo(i2c_address,[0x04, (dec2bcd(date))]);
  I2C1.writeTo(i2c_address,[0x05, (dec2bcd(month))]);
  I2C1.writeTo(i2c_address,[0x06, (dec2bcd(year))]);
}

DS3231.prototype.setTime = function(hour,minute) {
  I2C1.writeTo(i2c_address,[0x00, 0]);
  I2C1.writeTo(i2c_address,[0x01, (dec2bcd(minute))]);
  if (dstStatus === true) {
    I2C1.writeTo(i2c_address,[0x02, (dec2bcd(hour-1))]);
  }
  else
    I2C1.writeTo(i2c_address,[0x02, (dec2bcd(hour))]);
}

DS3231.prototype.setDay = function (val) {
  var days = ["Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"];
  var idx = days.indexOf(val);
  if (idx<0) {
    print("Not a valid day");
  }
  else {
    I2C1.writeTo(i2c_address,[0x03, (dec2bcd(1+idx))]);
 }
}

DS3231.prototype.setDstShift = function (hours) {
  dstShift = hours;
}

DS3231.prototype.readDateTime = function () {
  I2C1.writeTo(i2c_address, 0x00/* address*/);
  var data = I2C1.readFrom(i2c_address, 7/* bytes */); //read number of bytes from address
  var seconds = bcd2dec(data[0]);
  var minutes = (bcd2dec(data[1]));
  var hours = (data[2]);
  var dow = (bcd2dec(data[3]));
  var date = (bcd2dec(data[4]));
  var month = (bcd2dec(data[5]));
  var year = (bcd2dec(data[6]));

  if ((isDST(date,month,dow)) === true) {
    hours = bcd2dec((hours)+(dstShift));
    dstStatus = true;
  }
  else {
      hours = bcd2dec(hours);
    dstStatus = false;
  }

  rtcDate = date+"/"+month+"/"+year;
  rtcTime = hours+":"+minutes+":"+seconds;
  rtcDateTime = rtcDate+" "+rtcTime;
  rtcDay = dow;
  return rtcDateTime;
};