The aforementioned list of public holidays in South Africa for the calendar year 2023 contains the usual mention that "The Public Holidays Act (Act No 36 of 1994 [PDF]) determines whenever any public holiday falls on a Sunday, the Monday following on it shall be a public holiday", and contrary to 2 years ago, it lists 2 day in lieu public holidays to compensate the New Year's Day and Heritage Day public holidays falling on a Sunday.
As for Easter, the announcement states that "The dates on which Good Friday and Easter Sunday fall are determined according to the ecclesiastical moon. That varies each year but they fall at some point between late March and late April.".
Links and References
Below are links to the news stories referred to in the above "South African 2023 Public Holidays Announced" news story, as well as links to subsequents news stories which refer to the present news story.