Formal:
* Dydd da i chi. (deeth da ee khee) - This is the most formal way to say it, literally meaning "good day to you."
* Cawsoch ddydd da. (kowsoch deeth da) - This means "have a good day" and is slightly less formal than "Dydd da i chi."
Informal:
* Cael di ddydd da. (kayl dee deeth da) - This is a more casual way to say it, meaning "have you a good day?"
* Dydd da! (deeth da) - This is a very informal way to say "have a nice day" and can be used with close friends or family.
Other options:
* Mwynhewch y dydd! (mweenhewch eh deeth) - This means "Enjoy the day!" and is a good option for a slightly more enthusiastic greeting.
* Rhowch chi sylw i chi eich hun. (rowch khee sylew ee khee eh hun) - This means "Take care of yourself" and is a good way to say goodbye.
Choosing the right phrase:
The best way to choose the right phrase is to consider the context. If you're talking to someone you don't know well, it's best to use a more formal phrase like "Dydd da i chi." If you're talking to a friend or family member, you can use a more informal phrase like "Cael di ddydd da."