(TECH) watch with LED Matrix

Hi everyone,
Since I am a newbie I have a lot of questions and this is one of them: can I make a “watch” (display time, etc.) with RePhone GSM+Ble module? I will use a LED Matrix as a display and not a screen, also to be coded in Arduino IDE. I am asking because on internet all the watch projects are using some “crystal” add on to keep track of time so is this possible with the RePhone as is or the crystal needs to be added as external hardware …

Thanks! for guidance