How to keep millis() at 0? - arduino

Question

I'm making an Arduino reverse stopwatch..but Seems to have a problem with millis() function
Whenever I upload the code on Arduino the millis starts running itself..how can I keep it at 0 until I call the millis. or any alternatives to solve it...
#include "SevSeg.h"
int button1 = 11;
int button2 = 12;
int button3 = 13;
int value = 10;
int timer = 0;
bool n = true;
SevSeg Display;
void setup() {
Serial.begin(9600);
byte numDigits = 2;
byte digitPins[] = {9,8};
byte segmentPins[] = {10,2, 3, 4, 5, 6, 7,1};
bool resistorsOnSegments = true;
bool updateWithDelays = true;
byte hardwareConfig = COMMON_ANODE;
Display.begin(hardwareConfig, numDigits, digitPins, segmentPins, resistorsOnSegments);
Display.setBrightness(100);
}
void loop() {
Display.setNumber(value, 1);
Display.refreshDisplay();
if (digitalRead(11)==HIGH){
Start(value);
}
}
void Start(int value){
while(n){
unsigned long timerGlobal = millis();
Display.setNumber(value-timerGlobal/1000, 1);
Display.refreshDisplay();
if ((value-timerGlobal/1000) == 0){
n = false;
}
}
}

Answer 1

In arduino UNO
extern volatile unsigned long timer0_millis;
noInterrupts ();
timer0_millis = 0;
interrupts ();
But it makes no sense at all.
Simply remember the previous millis and calculate time passed (by substracting).

Answer 2

This should work
//#include "SevSeg.h"
int button1 = 11;
int button2 = 12;
int button3 = 13;
int value = 10;
int timer = 0;
bool n = true;
//Added
int currentTime = 0;
long int t0 = 0;
long int t1 = 0;
//SevSeg Display;
void setup() {
Serial.begin(9600);
byte numDigits = 2;
byte digitPins[] = {9,8};
byte segmentPins[] = {10,2, 3, 4, 5, 6, 7,1};
bool resistorsOnSegments = true;
bool updateWithDelays = true;
//byte hardwareConfig = COMMON_ANODE;
//Display.begin(hardwareConfig, numDigits, digitPins, segmentPins, resistorsOnSegments);
//Display.setBrightness(100);
}
void loop() {
//Display.setNumber(value, 1);
// Display.refreshDisplay();
if (digitalRead(11)==HIGH){
Start(value);
}
}
void Start(int value){
t0 = millis();
while(n){
t1 = millis();
if(t1 > (1000+t0)){
//has passed 1 second
currentTime++;
if(value-currentTime == 0){
n = false;
}
}
unsigned long timerGlobal = t1-t0;
//Display.setNumber(value-timerGlobal/1000, 1);
//Display.refreshDisplay();
}
}

Answer 3

Just implement a function that subtract the current millis from the previous millis()
The arduino millis() function is not a function that starts a timer. The millis function is meant to get the elapsed milliseconds since the program started.
Keep in mind that the millis() value will overflow afther:
50 days and 70 minutes. so afther this time the millis() will return 0 again and start over again.
You could implement your own timer using interrupts on the arduino. But like a good programmer always say's if something already exits why make it again? just use the millis() and subtract the current from the previous. But keep in mind of the overflow.