Time of the Easter Vigil
The Vigil, by its very nature, must take place at night. It is not begun before nightfall and should end before daybreak on Easter Sunday.
Pastoral planners should contact local weather stations for the time sunset will occur. Another 45 minutes or 1 hour should be added to that time to determine the approximate time for nightfall. (USCCB - The Roman Missal and The Easter Vigil)
Sacred Paschal Triduum resources from the USCCB
Easter resources from the USCCB