[1.15.2] Making a sword stronger at night

How do I make my sword deal more damage at night? I don't really care, if it's a strength buff, or a stat change, i just want it to be stronger. I tried doing this, but it didn't really help:
 

@Override
public void onUsingTick(ItemStack stack, LivingEntity player, int count) {
    if(player.getEntityWorld().getDayTime() >= 13000 && player.getEntityWorld().getDayTime() <= 18000) {
        player.addPotionEffect(new EffectInstance(Effects.STRENGTH, 5, 2));
    }
}