How long for USPS to deliver my order?

So i ordered my graduationd dress online on june 13th and the store is in new york city. they just shipped it out today and I live in toronto Canada. The class of shipping is called Priority Mail International Parcels...how long until I get my dress? because my graduation is june 28th and I MUST have it before then...i need to fit it and everything :( this is making me very anxious...