I'm not sure what time my event will start or end. Is this information required when creating an event?

Not at all. If you do not know when your event will begin or end, you can work around the start and end time by enabling the All day toggle by tapping it. This will remove the time slots from your event. When you figure out what time your event will begin and what time it will end, you can go back and disable the All day toggle to enter the start and end time.