[Abagail]

You can do something like this, maybe?

pawn Код:

public OnVehicleCreation(vehicleid)
{
    new day;
    Born[vehicleid] = getdate(day, day, day);
    return true;
}

stock GetCarAge(vehicleid)
{
    new tmpage, day;
    tmpage = Born[vehicleid] - getdate(day, day, day);
    return tmpage;
}

Something like this? Or, if it's purely MySQL then see event scheduling,
https://sampforum.blast.hk/showthread.php?pid=3258877#pid3258877