Do i HAVE to start SEASONIQUE on a sunday?

ok so i got seasonique and my doctor said to start it on the first day of my cycle (first day of my period but the thingy says to start it on a sunday. todays wendsday, and my doctor said that if i wait like 4 days after my period starts till the sunday then i will be unprotected untill about 2 weeks in. can i just start it today? like wh does it matter whether or not its a sunday