Yes, from what I recall there are 3 different times per seating. You get to choose main or late seating, Disney then allocates one of 3 times in that seating to you. You find out what time you've been given when you board the ship along with your restaurant rotation. All of this information is found on the dining tickets left in your cabin on the embarkation day. You need to take the tickets with you on the first night as they also have your table number. Irrespective of which restaurant you are scheduled to eat in, you will always have the same table number and dining time. I think they have 3 "start" times per seating as there are 3 restaurants and they stagger it to ease congestion in communal areas for cruisers and to make it easier on the galley.
According to Passporter, main dining is typically 5:30 pm, 5:45 pm and 6 pm; whereas late is 8 pm, 8:15 pm and 8:30 pm. We've had late dining in the past and have had 8:15 pm and 8:30 pm as our allocated times. Your stateroom host and servers will remind you each day which restaurant to go to for the next evening meal, in case you misplace the tickets with the dining rotation on them.