1. A day characterized by multiple unfortunate events, failures, or misfortunes affecting a specific person
After losing my job and my car breaking down, it was a disastrous day for me.
Depois de perder meu emprego e meu carro quebrar, foi um dia desastroso para mim.
2. A particularly bad or unlucky day for someone
It turned out to be a disastrous day for you with all those mistakes.
Acabou sendo um dia desastroso para você com todos esses erros.