Jonekl3... just to add what others have already said....
Dinner service in the Main Dining Room has 3 types of seating : Early (ie: 6PM), Late (ie: 8PM) and Anytime Dining. You select which you want at the time you book your cruise. There are advantages and disadvantages to all three, depending upon your needs. You need not worry about missing shows, as most show times are staggered and repeated so that all passengers have an opportunity to see them, regardless of dinner service. For families with kids, Early Seating is often the right choice, as kids tend to want to eat early. However, on port days, this may mean you have to rush back to the ship in order to change and get to the MDR on time. Late seating is often the choice of those without kids, and means you are not rushing back to the ship – but you eat late. And Anytime Dining is just that – you are seated anytime you wish while the MDR is open for service. Early and Late seating are assigned seating and assigned tables. This means you will eat with other passengers (and the same passengers) each night. It is a great way to meet others on the cruise, and life-long friendships have been made this way.
Conversely, you may also be seated the entire cruise with people you don’t particularly like or enjoy. Anytime Dining is somewhat “open seating” – meaning they may seat you at a table by yourself, or it may be with others… but it differs each night, depending upon what table is available at the time you arrive. With Anytime Dining, if you request, you can often be seated by yourself if a table is available). Anytime Dining offers great flexibility, but you may also have to wait several minutes for a table.
If you select Early or Late seating, you need to arrive in the MDR on time. Being 10 minutes late is acceptable, but late more than 10 minutes is not, and some people have been refused seating for being late. The dinner staff have this down to a science, and a late arrival can throw off service for the whole table. Be on time. If you are running late, it is probably best to just have dinner in the buffet.