button interrupt

I have designed and printed a stepper driven clock and have the following issue.

This section of code works fine.
The second hand advances every second and if i press my 'advance button' the clock moves forwards by one minute.

void MOVE_TIME() {
  byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
  readDS3231time(&second, &minute, &hour, &dayOfWeek, &dayOfMonth, &month, &year);
  ss = second;
  buttonState = digitalRead(buttonPin);
  if (buttonState == HIGH) {
    for ( int count = 1; count <= 9600; count++) {
      digitalWrite(Y_DIR_PIN    , LOW);
      digitalWrite(Y_STEP_PIN    , HIGH);
      delay(1);
      digitalWrite(Y_STEP_PIN    , LOW);

    }

  }

  if (ss != ssold) {              //ONLY CONTINUE IF THE SECONDS HAVE CHANGED

    for ( int count = 1; count <= 160; count++) { //forwards CW
      digitalWrite(Y_DIR_PIN    , LOW);
      digitalWrite(Y_STEP_PIN    , HIGH);
      delay(Y_SPEED);
      digitalWrite(Y_STEP_PIN    , LOW);
    }
    ssold = ss;                     

  }
}

My question is, why will the advance button NOT work if i use the following code?

void MOVE_TIME() {
  byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
  readDS3231time(&second, &minute, &hour, &dayOfWeek, &dayOfMonth, &month, &year);
  ss = second;
  buttonState = digitalRead(buttonPin);
  if (buttonState == HIGH) {
    advance_time;

  }

  if (ss != ssold) {              //ONLY CONTINUE IF THE SECONDS HAVE CHANGED

    for ( int count = 1; count <= 160; count++) { //forwards CW
      digitalWrite(Y_DIR_PIN    , LOW);
      digitalWrite(Y_STEP_PIN    , HIGH);
      delay(Y_SPEED);
      digitalWrite(Y_STEP_PIN    , LOW);
    }
    ssold = ss;

  }
}

void advance_time() {
  for ( int count = 1; count <= 3200; count++) {
    digitalWrite(Y_DIR_PIN    , LOW);
    digitalWrite(Y_STEP_PIN    , HIGH);
    delay(1);
    digitalWrite(Y_STEP_PIN    , LOW);

  }
}

When the button is pressed it will not run the advance_time routine

Because advance_time in below is not a function call ??

  if (buttonState == HIGH) {
    advance_time;

  }

parenthesis are important:

advance_time();