Count-Up Timer on ESP8266 and I2C LCD

I need a count-up timer on the desk so that I can do a presentation without turning my head to the wall clock. So I wrote one with ESP8266 and I²C-connected LCD unit.

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x3F, 16, 2);

void
setup()
{
  lcd.begin(16, 2);
  lcd.init();
  lcd.backlight();
}

void
loop()
{
  int seconds = millis() / 1000;
  int minutes = seconds / 60;
  seconds %= 60;

  lcd.clear();
  lcd.print(minutes);
  lcd.print(':');
  if (seconds < 10) {
    lcd.print('0');
  }
  lcd.print(seconds);
  delay(100);
}

Hardware is Losant LCD Kit. I'm using Marco Schwartz's LiquidCrystal_I2C library.