These are the five key events:
The first sighting of the three ships will be from Ryde on the Isle of Wight before dawn, at 3.25 a.m., when Queen Victoria passes, after which they will sail, 15 minutes apart, along the Solent and up Southampton Water, accompanied by fire tugs and a flotilla of small boats. Between 6 a.m. and 6.15 a.m., Queen Elizabeth and Queen Victoria will position bow-to-bow near City Terminal and Queen Mary 2 will pass each ship in turn, crews of all three lining the foredecks, for a three-bow formation; essentially, a big photo opportunity for the media, as spectators won't be able to get close enough.
The ships will then dock: Queen Mary 2 at Ocean Terminal, Queen Victoria at Mayflower Terminal and Queen Elizabeth at City Terminal. All three ships will be disembarking and embarking passengers throughout the day.
From midday, there will be a free festival in Mayflower Park with live bands, choirs, dance demonstrations and classes, foods from around the world, arts and crafts stalls and a fairground. The event is timed to coincide with Cunard's celebrations and ends at 11 p.m. when the ships sail.
At 6.20 p.m., the Red Arrows will fly the length of the docks in a 25-minute display. The best places to watch both the aerial display and the fireworks will be Mayflower Park, Town Quay and Hythe Marina. For the fireworks, the three ships will position together next to City Terminal to create the backdrop for the display. All three sail together at 11 p.m., Queen Mary 2 leading her sisters down Southampton Water and out into the Solent.
Cunard will be running its own radio programme, Cunard FM, for the day, broadcasting on 87.7 FM from 8 a.m. to midnight with music, celebrity interviews and live commentary of the events, as well as the musical soundtrack to the fireworks display. But you'll have to be within 3km of Carnival House in Southampton to pick up the signal.
We'll be reporting on the day from the dawn arrival to the events of the evening, so check our Twitter feed and Facebook page for live coverage of the events.
--by Sue Bryant, Cruise Critic Contributing Editor