How to change from Traditional Dining to My Time Dining? (Most people don’t know this trick)
In:You booked your cruise and chose a dining option for dinner, but now you want to change it. That sounds like an easy change to request, but what if it's not available anymore?

Royal Caribbean offers two types of dinner choices when you book a cruise as it relates to the Main Dining Room: Traditional and My Time Dining.
The closer you get to your cruise, you might find limited options left for switching from one to other. Perhaps a particular traditional dinner seating is not available. Or My Time Dining might be sold out. Is there any chance to change it?
There are a few options you could try, including one that new cruisers are completely unaware of exists.
First, try to get on a waitlist

If there's a few months left before your cruise departs, I'd start off by getting on the waitlist for the dining time or option you prefer.
Royal Caribbean has a wait list of a specific dining option, so if you're told it's sold out, ask to be on that waitlist.
You can ask your travel agent to be put on the waitlist. If you booked directly with Royal Caribbean, call in and ask for it.
Sometimes even the waitlist is temporarily filled. Don't worry though! If the waitlist time you want is unavailable and the cruise is more than a few weeks out call back in a week or two and try again.

These waitlists work exactly as you might imagine: someone cancels their cruise or changes to a different dining option, and the next person on the waitlist gets moved to the open slot.
In my experience, the waitlist comes through in most cases, but it helps the earlier you get put on it.
Be aware if the waitlist comes through, there's not really a notification of any kind that I'm aware of. Instead, it just changes and it's up to you to check periodically to see if the change has been made.
If that fails, try this trick on the ship

If the waitlist doesn't work, don't fret, because there's a fallback that always seems to work.
Once you board your ship on the first day, head to the Main Dining Room after lunch. Anytime after 1pm should suffice.
Ask to speak to the Head Waiter that is on duty. Alternatively, there is sometimes a desk set up that says "Dining Changes" or something to that effect. Either option will work.

At this point, politely explain the situation and ask if you can have your dining option changed.
In my experience, this usually works. Either someone else has done the same thing and opened up a spot, or the ship simply has more capacity than the shoreside system allows to book.
In any case, I'd be pretty surprised to hear if this fallback didn't work.
Which is better: My Time Dining or Traditional?

Royal Caribbean offers the choice of My Time Dining and Traditional dinner so passengers can find the best choice for them.
Each has its advantages, so it's a matter of what your own style is for how and when you'd like to eat.
Traditional dinner means you have a set time, table, waiter, and table mates. It has less flexibility since your schedule is set, but it's also simpler and there's no waiting for a table.

My Time Dining is flexible, and allows you to eat early or late depending on your plans.
The issue with My Time Dining is you may have to wait for a table, and you should make reservations in advance to reduce a wait. Making reservations seems to take away from the notion of being flexible, to some degree.
I always pick Traditional

If you're looking for an opinion on what to choose, I usually go with Traditional.
Since my first Royal Caribbean cruise more than a decade ago, I've chosen Traditional dinner times because of how straight forward it is.
The reason I don't love My Time Dining is that there's a wait for a table, or at least a short line. I really like the convenience of not having to make reservations or wait in line, even if it means a rigid dining schedule.
Plus, I really like having the same waiters each night. I think creating a rapport with them adds to the experience because it makes it's friendly and fun, especially when you have waiters with a good personality.