Problem w/ interaction with computer

So i’ve started a project : basically it’s an arduino with some sensor, and I want to gather the data a few days later.
Problem : the arduino won’t start until i started the comm console on computer.

I’ve put a Serial.print in the setup, is it that witch is stopping the arduino to go further ?

Ps : any ideas to turn the millis() into DD:HH:SS

Thanks by advance

I've put a Serial.print in the setup, is it that witch is stopping the arduino to go further ?

No. Something else in the code you didn't post is causing the problem.

Ps : any ideas to turn the millis() into DD:HH:SS

The value returned by millis() is the number of milliseconds since the Arduino started. Without knowing what date and time that happened, the value from millis() can NOT be turned into a date/time string. Day:Hour:Second is a VERY strange way of representing a date/time value...

It is basically from when it started eg : 01:25:47 from when it started

Sorry to not post this earlier but here is the code :

(i’m using an arduino nano)

test_2.ino (1.63 KB)