real time clock drifting off

Hey everyone,
I'm using the Espruino Pico's real time clock for my clock project. Basically when I press the button, the Pico shows the time on some 7-segment LEDs for about a second and goes back to deep sleep.

function data() {
  full=(new Date()).toString();
  words = full.split(' ');
  month = words[1];
  date = words[2];
  bigtime = words[4];
  small = words[4].split(':');
  hour = small[0];
  if (hour > 12) {
    hour = hour-12;
  }
  min = small[1];
}

function hourDriver(){
data();
switch(Number(hour)) {
  //some code
  }
}

function minuteDriver(){
data();
switch(Number(min)) {
  //some code
  }
}

setWatch(function (e) {
  data();
  for(i=0;i<60;i++){hourDriver();minuteDri­ver();}
  allClear(); //initializes 7-segment display
  setDeepSleep(1);
}, B8, {edge:"falling", repeat:true, debounce:50});

No matter what I do, the time seems to be drifting off about 5 to 10 minutes after a full day of use. What did I do wrong??? Or is the Pico's clock not the most accurate?

Thanks!

If you want the entire code it's in the comment below.