Monterosso Al Mare (Cinque Terre) Fireworks: Aug. 14 or 15?

I am planning to arrive to CT on Aug. 14 and RS book says that fireworks are on that day but when I asked people at the hotel I will be staying they say they are displayed on Aug. 15. Does anyone know when are they suppose to be display? I would like to know the exact day because it would define whether I would stop by Pisa on the way to CT. Thanks,
Lydia