Reference > Language > Functions > Time > Millis

millis()

[Time]

Description

Returns the number of milliseconds since the Arduino board began running the current program. This number will overflow (go back to zero), after approximately 50 days.

Syntax

time = millis()

Parameters

Nothing

Returns

Number of milliseconds since the program started (unsigned long)

Example Code

The code reads the milllisecond since the Arduino board began.

unsigned long time;

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

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

Notes and Warnings

Please note that the return value for millis() is an unsigned long, logic errors may occur if a programmer tries to do arithmetic with smaller data types such as int’s. Even signed long may encounter errors as its maximum value is half that of its unsigned counterpart.