Time.deltaTime at a specific moment

Let’s say I have a time counter. And I want to do:

public double myCounter;

void Update(){
    myCounter += Time.deltaTime;

    if(myCounter == 1.453693d){
       doThing();
    }
}

However myCounter will never be 1.453693 because there’s a skipping of time when it’s doing the sum.

How can I make this work?

Instead of doing that a substitute for it is the following:

void Start ()
{
    StartCoroutine(Timer());
}

IEnumerator Timer ()
{
    yield return new WaitForSeconds(1.453693);
    doThing();
}