---
title: millis()
categories: [ "Functions" ]
subCategories: [ "Time" ]
---

= millis()

// OVERVIEW SECTION STARTS
[#overview]
--

[float]
=== Description
Returns the number of milliseconds passed since the Arduino board began running the current program. This number will overflow (go back to zero), after approximately 50 days.
[%hardbreaks]


[float]
=== Syntax
`time = millis()`


[float]
=== Parameters
None


[float]
=== Returns
Number of milliseconds passed since the program started. Data type: `unsigned long`.

--
// OVERVIEW SECTION ENDS




// HOW TO USE SECTION STARTS
[#howtouse]
--

[float]
=== Example Code
// Describe what the example code is all about and add relevant code   ►►►►► THIS SECTION IS MANDATORY ◄◄◄◄◄
This example code prints on the serial port the number of milliseconds passed since the Arduino board started running the code itself.

[source,arduino]
----
unsigned long myTime;

void setup() {
  Serial.begin(9600);
}
void loop() {
  Serial.print("Time: ");
  myTime = millis();

  Serial.println(myTime); // prints time since program started
  delay(1000);          // wait a second so as not to send massive amounts of data
}
----
[%hardbreaks]

[float]
=== Notes and Warnings

* The return value for millis() is of type `unsigned long`, logic errors may occur if a programmer tries to do arithmetic with smaller data types such as `int`. Even signed `long` may encounter errors as its maximum value is half that of its unsigned counterpart.
* millis() is incremented (for 16 MHz AVR chips and some others) every 1.024 milliseconds, then incrementing by 2 (rather than 1) every 41 or 42 ticks, to pull it back into synch; thus some millis() values are skipped. For accurate timing over short intervals, consider using micros().
* millis() will wrap around to 0 after about 49 days (micros in about 71 minutes). 
* Reconfiguration of the microcontroller's timers may result in inaccurate `millis()` readings. The "Arduino AVR Boards" and "Arduino megaAVR Boards" cores use Timer0 to generate `millis()`. The "Arduino ARM (32-bits) Boards" and "Arduino SAMD (32-bits ARM Cortex-M0+) Boards" cores use the SysTick timer.

--
// HOW TO USE SECTION ENDS


// SEE ALSO SECTION
[#see_also]
--

[float]
=== See also

[role="example"]
* #EXAMPLE# http://arduino.cc/en/Tutorial/BlinkWithoutDelay[Blink Without Delay^]

--
// SEE ALSO SECTION ENDS