printing the time for Status High for LED In UNO

Hi i am currently doing my final year bachelors project and building a automated streetlight And i want to know the amount of time the Led stays on after the motion sensor is triggered, Searched many places tried codes but couldnt do it. Would be great if someone can help me

Here is my code for which i want to know the amount of time LED is on
I tried to use pulseIn but couldnt figure it out. Plus i am a beginner.

int LED = 13;
int PIR = 7;


void setup() {
   Serial.begin(9600);
  pinMode(LED,OUTPUT); //gives output according to pir sensor
 pinMode(PIR,INPUT); // takes input ie motion
  
}

void loop() {
int value = digitalRead(PIR);

 if (value == 1){
    digitalWrite(LED, HIGH);

     
    }
 else {
  digitalWrite(LED, LOW);
  Serial.println("NO motion");
   }

Save the value of millis() value becomes equal to 1 and the LED turns on
Save the value of millis() when the LED turns off

The difference is the time in milliseconds that the LED was on