Daat Zkenim on Exodus
1 א

ואלה שמות הבאים. והלא כבר באו קודם לכן אלא קודם שמת יוסף לא נתן עליהם מסים משמת נתן עליהם ונעשה כאלו בו ביום באו:

ואלה שמות וגו....הבאים, “and these are the names, etc........who arrived in Egypt ” why is that verse written in the present tense, seeing that it was quite some time since Yaakov and his sons had arrived in Egypt? They had been there long before the death of Joseph. The reason that they are referred to as new arrivals was that as long as Joseph was alive they did not have to pay any taxes. As soon as he had died they became subject to normal taxation. Therefore they considered that day as if it was the day that they had arrived there. (Sh’mot Rabbah 1,4)