1. An ideal or flawless day tailored to someone's preferences, desires, or needs
A perfect day for you would include sleeping in and spending time at the beach.
Um dia perfeito para você incluiria dormir até tarde e passar tempo na praia.
2. A day when everything goes exactly as someone wishes
After winning the lottery, he had a perfect day for himself.
Depois de ganhar na loteria, ele teve um dia perfeito para si.