Formal:
* Geniet jou dag! (Enjoy your day!) - This is the most literal and formal translation.
* Goeie dag verder! (Good day further!) - This is a bit more formal than the previous option, and implies that the day has already started.
Informal:
* Lekker dag! (Nice day!) - This is a casual and friendly way to say "have a nice day".
* Maak 'n lekker dag! (Make a nice day!) - This is a bit more encouraging and implies that the person has the power to have a good day.
Other options:
* Totsiens! (Goodbye!) - This can be used as a general farewell and often implies that you hope the person has a nice day.
* Sien jou weer! (See you again!) - This is a friendly way to say goodbye and can be used as a way to wish someone a good day.
The best option to use will depend on the context and your relationship with the person you're talking to.