JeeLabs Precision RTC Module

Starting to get to grips with this now.
It's probably not very elegant but the following seems to be working from what I can see. Any comments greatly appreciated good or bad.

I2C1.setup({scl:B6,sda:B7});
var rtcTime = '';
var rtcDate = '';
var rtcDateTime = '';
var dstStatus = '';
var dstShift = 1;
i2c_address = 0x68;

function readDateTime() {
  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;
  return;
}

function setDate(date,month,year) {
  I2C1.writeTo(i2c_address,[0x04, (dec2bcd(date))]);
  I2C1.writeTo(i2c_address,[0x05, (dec2bcd(month))]);
  I2C1.writeTo(i2c_address,[0x06, (dec2bcd(year))]);
}

function setTime(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))]);
}

function setDay(val) {
  switch (val.toString) {
    case "Monday":
      I2C1.writeTo(i2c_address,[0x03, (dec2bcd(1))]);
      break;
    case "Tuesday":
      I2C1.writeTo(i2c_address,[0x03, (dec2bcd(2))]);
      break;
    case "Wednesday":
      I2C1.writeTo(i2c_address,[0x03, (dec2bcd(3))]);
      break;
    case "Thursday":
      I2C1.writeTo(i2c_address,[0x03, (dec2bcd(4))]);
      break;
    case "Friday":
      I2C1.writeTo(i2c_address,[0x03, (dec2bcd(5))]);
      break;
    case "Saturday":
      I2C1.writeTo(i2c_address,[0x03, (dec2bcd(6))]);
      break;
    case "Sunday":
      I2C1.writeTo(i2c_address,[0x03, (dec2bcd(7))]);
      break;
    default:
      print(text,"Not a valid day");
    return;
  }
}

//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;
    }


// 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);
}

setInterval(readDateTime, 500);