Use millis to display real time

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How do I use millis() to display a real time clock? Just a simple hh:mm:ss:ms time display. ms is the milliseconds for every second. If it works without millis then thats fine too!

Many thanks


There are numerous examples in this forum. has lots of resources (examples, tutorials, references…).

This is in the references:



Thank you very much! Just quickly millis() gives me a four digit number that is updating with the left most number being the number of seconds. Do you know how I can get the number that is second from the left only? For example, if the current time is 2345, I just want to get the number 3. Many thanks!

divide by 1000 using integer math (no remainder\decimal points) to get the seconds.

Think about the rest… using division, multiplication and subtraction to extract each digit.

This is simple math and worthwhile for you to work through.

You could convert to a string and use String functions:
You need to think about the size of the string… you will have more digits as millis() gets larger.

Use println() and experiment…

void setup() 
  size(200, 200);
  frameRate(1); //Slow things down. Not millis() though!

void draw() 
  int t = millis();
  println(t/1); // :)


millis has nothing to do with the TIME. millis() is just the timespan passed since the Sketch started. It is not something like 7:45 a.m.

To get the TIME use hours(), minute(), second() etc.

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Do you know how to split a number with no spaces? For example the number 1234, how would I get the 2? the function split() wont work because it separates a list of numbers with spaces. Many thanks

On the subject of extracting a digit by its decimal weight from an integer number…

There is also the % modulo operator… look it up in the reference.

Try to do this with math first and then write some code.

How would you do it?


If your intent is to have a real-time clock, the recommendation to use the Time & Date functions from the reference is the easiest option. If you want to display a digital clock accurate to the millisecond, the modulo and division operators are your best friends. This method for a stopwatch app I made takes in milliseconds as an input and returns a String as an output, with the String being formatted hh:mm:ss:ms

String timeFormat(int millis) {
  String t = "";
  int hours = millis / 3600000;
  //there are 3600000 milliseconds in 1 hour, so integer division will produce the number of hours
  int minutes = (millis % 3600000) / 60000;
  //there are 60000 milliseconds in 1 minute, but it will not suffice to simply divide, as the number of hours needs to be disregarded when counting minutes.
  //This is done through the modulo operator (%). Modulo returns the remainder of a division operation.
  //Without the modulo, when the minutes pass 59, the minute will count 60, 61, etc.
  //But, with the modulo, when minutes pass 59, the number of milliseconds used to calculate minutes resets to zero, which is the intended behavior of the clock.
  int seconds = (millis % 60000) / 1000;
  //The same logic is applied to seconds and milliseconds.
  int milliseconds = millis % 1000;
  //The rest is just string formatting
  t += hours + ":";
  if (minutes < 10) {
    t += "0";
  t += minutes + ":";
  if (seconds < 10) {
    t += "0";
  t += seconds + ".";
  if (milliseconds < 10) {
    t += "00";
  } else if (milliseconds < 100) {
    t += "0";
  t += milliseconds;
  return t;

If you want to use this function, you’ll have to look elsewhere to find how to get a real-time millisecond count, and you may have to adjust the method to take a long as an input instead of an integer.